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	$152.93	13.588%	$173.7101	$173.71	$173.70	$173.70
Purchase #2	$142.69	11.358%	$158.8967	$158.90	$158.90	$158.90
Purchase #3	$44.65	13.468%	$50.6635	$50.66	$50.65	$50.70
Purchase #4	$145.89	13.429%	$165.4816	$165.48	$165.50	$165.50
Purchase #5	$10.27	9.273%	$11.2223	$11.22	$11.20	$11.20
Purchase #6	$31.31	11.516%	$34.9157	$34.92	$34.90	$34.90
Purchase #7	$34.54	9.704%	$37.8918	$37.89	$37.90	$37.90
7 purchase totals =	$562.28		$632.7817	$632.78	$632.75	$632.80