Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$38.40	8.122%	$41.5188	$41.52	$41.50	$41.50
Purchase #2	$93.29	7.749%	$100.519	$100.52	$100.50	$100.50
Purchase #3	$243.27	9.784%	$267.0715	$267.07	$267.05	$267.10
Purchase #4	$242.35	3.678%	$251.2636	$251.26	$251.25	$251.30
Purchase #5	$97.82	4.483%	$102.2053	$102.21	$102.20	$102.20
Purchase #6	$195.94	7.130%	$209.9105	$209.91	$209.90	$209.90
Purchase #7	$44.34	3.392%	$45.844	$45.84	$45.85	$45.80
7 purchase totals =	$955.41		$1,018.3327	$1,018.33	$1,018.25	$1,018.30