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	$145.84	7.153%	$156.2719	$156.27	$156.25	$156.30
Purchase #2	$236.73	7.550%	$254.6031	$254.60	$254.60	$254.60
Purchase #3	$200.88	12.562%	$226.1145	$226.11	$226.10	$226.10
Purchase #4	$10.53	9.827%	$11.5648	$11.56	$11.55	$11.60
Purchase #5	$128.90	7.740%	$138.8769	$138.88	$138.90	$138.90
Purchase #6	$239.89	6.709%	$255.9842	$255.98	$256.00	$256.00
Purchase #7	$98.50	13.486%	$111.7837	$111.78	$111.80	$111.80
7 purchase totals =	$1,061.27		$1,155.1991	$1,155.18	$1,155.20	$1,155.30