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	$59.50	13.336%	$67.4349	$67.43	$67.45	$67.40
Purchase #2	$217.27	4.426%	$226.8864	$226.89	$226.90	$226.90
Purchase #3	$66.43	8.606%	$72.147	$72.15	$72.15	$72.10
Purchase #4	$242.28	10.312%	$267.2639	$267.26	$267.25	$267.30
Purchase #5	$63.69	12.335%	$71.5462	$71.55	$71.55	$71.50
Purchase #6	$85.42	9.351%	$93.4076	$93.41	$93.40	$93.40
Purchase #7	$15.69	4.808%	$16.4444	$16.44	$16.45	$16.40
7 purchase totals =	$750.28		$815.1304	$815.13	$815.15	$815.00