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	$62.89	13.244%	$71.2192	$71.22	$71.20	$71.20
Purchase #2	$99.38	12.625%	$111.9267	$111.93	$111.95	$111.90
Purchase #3	$127.94	13.200%	$144.8281	$144.83	$144.85	$144.80
Purchase #4	$16.46	9.508%	$18.025	$18.03	$18.05	$18.00
Purchase #5	$21.41	5.327%	$22.5505	$22.55	$22.55	$22.60
Purchase #6	$105.74	5.840%	$111.9152	$111.92	$111.90	$111.90
Purchase #7	$246.98	4.526%	$258.1583	$258.16	$258.15	$258.20
7 purchase totals =	$680.80		$738.6230	$738.64	$738.65	$738.60