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	$115.91	9.665%	$127.1127	$127.11	$127.10	$127.10
Purchase #2	$59.95	3.645%	$62.1352	$62.14	$62.15	$62.10
Purchase #3	$41.26	10.286%	$45.504	$45.50	$45.50	$45.50
Purchase #4	$142.39	8.574%	$154.5985	$154.60	$154.60	$154.60
Purchase #5	$9.90	13.759%	$11.2621	$11.26	$11.25	$11.30
Purchase #6	$138.85	3.629%	$143.8889	$143.89	$143.90	$143.90
Purchase #7	$243.53	4.264%	$253.9141	$253.91	$253.90	$253.90
7 purchase totals =	$751.79		$798.4155	$798.41	$798.40	$798.40