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	$96.70	12.251%	$108.5467	$108.55	$108.55	$108.50
Purchase #2	$68.34	5.213%	$71.9026	$71.90	$71.90	$71.90
Purchase #3	$33.37	13.135%	$37.7531	$37.75	$37.75	$37.80
Purchase #4	$38.94	4.679%	$40.762	$40.76	$40.75	$40.80
Purchase #5	$35.31	3.682%	$36.6101	$36.61	$36.60	$36.60
Purchase #6	$5.28	10.664%	$5.8431	$5.84	$5.85	$5.80
Purchase #7	$234.61	12.587%	$264.1404	$264.14	$264.15	$264.10
7 purchase totals =	$512.55		$565.5580	$565.55	$565.55	$565.50