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	$69.52	4.395%	$72.5754	$72.58	$72.60	$72.60
Purchase #2	$126.96	13.442%	$144.026	$144.03	$144.05	$144.00
Purchase #3	$76.74	10.834%	$85.054	$85.05	$85.05	$85.10
Purchase #4	$91.85	8.588%	$99.7381	$99.74	$99.75	$99.70
Purchase #5	$159.25	5.343%	$167.7587	$167.76	$167.75	$167.80
Purchase #6	$156.48	12.394%	$175.8741	$175.87	$175.85	$175.90
Purchase #7	$159.81	3.406%	$165.2531	$165.25	$165.25	$165.30
7 purchase totals =	$840.61		$910.2794	$910.28	$910.30	$910.40