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	$74.25	3.296%	$76.6973	$76.70	$76.70	$76.70
Purchase #2	$182.57	5.561%	$192.7227	$192.72	$192.70	$192.70
Purchase #3	$165.50	4.111%	$172.3037	$172.30	$172.30	$172.30
Purchase #4	$133.50	6.736%	$142.4926	$142.49	$142.50	$142.50
Purchase #5	$90.72	6.250%	$96.39	$96.39	$96.40	$96.40
Purchase #6	$121.64	3.848%	$126.3207	$126.32	$126.30	$126.30
Purchase #7	$125.39	13.191%	$141.9302	$141.93	$141.95	$141.90
7 purchase totals =	$893.57		$948.8572	$948.85	$948.85	$948.80