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	$41.72	3.818%	$43.3129	$43.31	$43.30	$43.30
Purchase #2	$220.87	8.137%	$238.8422	$238.84	$238.85	$238.80
Purchase #3	$240.41	4.312%	$250.7765	$250.78	$250.80	$250.80
Purchase #4	$53.77	11.523%	$59.9659	$59.97	$59.95	$60.00
Purchase #5	$109.30	3.846%	$113.5037	$113.50	$113.50	$113.50
Purchase #6	$234.90	3.511%	$243.1473	$243.15	$243.15	$243.10
Purchase #7	$231.61	10.602%	$256.1653	$256.17	$256.15	$256.20
7 purchase totals =	$1,132.58		$1,205.7138	$1,205.72	$1,205.70	$1,205.70