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	$54.60	9.611%	$59.8476	$59.85	$59.85	$59.80
Purchase #2	$46.63	4.768%	$48.8533	$48.85	$48.85	$48.90
Purchase #3	$175.39	13.763%	$199.5289	$199.53	$199.55	$199.50
Purchase #4	$25.54	12.127%	$28.6372	$28.64	$28.65	$28.60
Purchase #5	$55.62	10.819%	$61.6375	$61.64	$61.65	$61.60
Purchase #6	$173.37	10.343%	$191.3017	$191.30	$191.30	$191.30
Purchase #7	$113.80	13.623%	$129.303	$129.30	$129.30	$129.30
7 purchase totals =	$644.95		$719.1092	$719.11	$719.15	$719.00