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	$235.38	12.503%	$264.8096	$264.81	$264.80	$264.80
Purchase #2	$19.95	9.112%	$21.7678	$21.77	$21.75	$21.80
Purchase #3	$102.51	9.390%	$112.1357	$112.14	$112.15	$112.10
Purchase #4	$228.37	12.390%	$256.665	$256.67	$256.65	$256.70
Purchase #5	$111.35	13.458%	$126.3355	$126.34	$126.35	$126.30
Purchase #6	$68.73	4.430%	$71.7747	$71.77	$71.75	$71.80
Purchase #7	$177.33	12.851%	$200.1187	$200.12	$200.10	$200.10
7 purchase totals =	$943.62		$1,053.6070	$1,053.62	$1,053.55	$1,053.60