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	$38.91	6.712%	$41.5216	$41.52	$41.50	$41.50
Purchase #2	$45.62	10.222%	$50.2833	$50.28	$50.30	$50.30
Purchase #3	$244.61	11.563%	$272.8943	$272.89	$272.90	$272.90
Purchase #4	$70.80	11.498%	$78.9406	$78.94	$78.95	$78.90
Purchase #5	$236.35	6.163%	$250.9163	$250.92	$250.90	$250.90
Purchase #6	$50.81	12.643%	$57.2339	$57.23	$57.25	$57.20
Purchase #7	$108.44	4.643%	$113.4749	$113.47	$113.45	$113.50
7 purchase totals =	$795.54		$865.2649	$865.25	$865.25	$865.20