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	$35.63	4.508%	$37.2362	$37.24	$37.25	$37.20
Purchase #2	$59.74	4.708%	$62.5526	$62.55	$62.55	$62.60
Purchase #3	$19.55	13.185%	$22.1277	$22.13	$22.15	$22.10
Purchase #4	$120.95	5.521%	$127.6276	$127.63	$127.65	$127.60
Purchase #5	$78.88	8.299%	$85.4263	$85.43	$85.45	$85.40
Purchase #6	$199.31	11.361%	$221.9536	$221.95	$221.95	$222.00
Purchase #7	$67.80	12.291%	$76.1333	$76.13	$76.15	$76.10
7 purchase totals =	$581.86		$633.0573	$633.06	$633.15	$633.00