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	$239.89	9.215%	$261.9959	$262.00	$262.00	$262.00
Purchase #2	$141.87	3.131%	$146.3119	$146.31	$146.30	$146.30
Purchase #3	$81.72	9.848%	$89.7678	$89.77	$89.75	$89.80
Purchase #4	$79.52	4.155%	$82.8241	$82.82	$82.80	$82.80
Purchase #5	$137.76	8.505%	$149.4765	$149.48	$149.50	$149.50
Purchase #6	$71.37	4.316%	$74.4503	$74.45	$74.45	$74.50
Purchase #7	$209.57	5.193%	$220.453	$220.45	$220.45	$220.50
7 purchase totals =	$961.70		$1,025.2795	$1,025.28	$1,025.25	$1,025.40