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	$82.76	10.385%	$91.3546	$91.35	$91.35	$91.40
Purchase #2	$127.87	12.530%	$143.8921	$143.89	$143.90	$143.90
Purchase #3	$9.33	11.689%	$10.4206	$10.42	$10.40	$10.40
Purchase #4	$59.75	11.442%	$66.5866	$66.59	$66.60	$66.60
Purchase #5	$43.90	4.240%	$45.7614	$45.76	$45.75	$45.80
Purchase #6	$18.89	5.136%	$19.8602	$19.86	$19.85	$19.90
Purchase #7	$232.43	6.146%	$246.7151	$246.72	$246.70	$246.70
7 purchase totals =	$574.93		$624.5906	$624.59	$624.55	$624.70