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	$52.84	9.468%	$57.8429	$57.84	$57.85	$57.80
Purchase #2	$91.60	5.555%	$96.6884	$96.69	$96.70	$96.70
Purchase #3	$65.81	9.512%	$72.0698	$72.07	$72.05	$72.10
Purchase #4	$37.34	5.330%	$39.3302	$39.33	$39.35	$39.30
Purchase #5	$249.52	5.488%	$263.2137	$263.21	$263.20	$263.20
Purchase #6	$106.45	12.251%	$119.4912	$119.49	$119.50	$119.50
Purchase #7	$99.81	12.143%	$111.9299	$111.93	$111.95	$111.90
7 purchase totals =	$703.37		$760.5661	$760.56	$760.60	$760.50