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	$174.68	6.200%	$185.5102	$185.51	$185.50	$185.50
Purchase #2	$60.76	9.511%	$66.5389	$66.54	$66.55	$66.50
Purchase #3	$64.60	4.829%	$67.7195	$67.72	$67.70	$67.70
Purchase #4	$79.46	5.327%	$83.6928	$83.69	$83.70	$83.70
Purchase #5	$26.66	10.149%	$29.3657	$29.37	$29.35	$29.40
Purchase #6	$28.72	13.217%	$32.5159	$32.52	$32.50	$32.50
Purchase #7	$149.48	10.788%	$165.6059	$165.61	$165.60	$165.60
7 purchase totals =	$584.36		$630.9489	$630.96	$630.90	$630.90