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	$134.35	9.151%	$146.6444	$146.64	$146.65	$146.60
Purchase #2	$157.74	10.405%	$174.1528	$174.15	$174.15	$174.20
Purchase #3	$147.98	12.770%	$166.877	$166.88	$166.90	$166.90
Purchase #4	$184.72	11.714%	$206.3581	$206.36	$206.35	$206.40
Purchase #5	$84.75	9.570%	$92.8606	$92.86	$92.85	$92.90
Purchase #6	$78.54	13.433%	$89.0903	$89.09	$89.10	$89.10
Purchase #7	$158.27	12.168%	$177.5283	$177.53	$177.55	$177.50
7 purchase totals =	$946.35		$1,053.5115	$1,053.51	$1,053.55	$1,053.60