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	$216.46	12.695%	$243.9396	$243.94	$243.95	$243.90
Purchase #2	$37.28	10.274%	$41.1101	$41.11	$41.10	$41.10
Purchase #3	$144.77	13.679%	$164.5731	$164.57	$164.55	$164.60
Purchase #4	$237.58	10.587%	$262.7326	$262.73	$262.75	$262.70
Purchase #5	$89.90	4.719%	$94.1424	$94.14	$94.15	$94.10
Purchase #6	$52.90	6.375%	$56.2724	$56.27	$56.25	$56.30
Purchase #7	$146.93	5.827%	$155.4916	$155.49	$155.50	$155.50
7 purchase totals =	$925.82		$1,018.2618	$1,018.25	$1,018.25	$1,018.20