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	$82.65	10.753%	$91.5374	$91.54	$91.55	$91.50
Purchase #2	$196.80	4.272%	$205.2073	$205.21	$205.20	$205.20
Purchase #3	$45.51	11.534%	$50.7591	$50.76	$50.75	$50.80
Purchase #4	$65.34	10.527%	$72.2183	$72.22	$72.20	$72.20
Purchase #5	$56.93	10.136%	$62.7004	$62.70	$62.70	$62.70
Purchase #6	$177.41	4.595%	$185.562	$185.56	$185.55	$185.60
Purchase #7	$237.54	10.816%	$263.2323	$263.23	$263.25	$263.20
7 purchase totals =	$862.18		$931.2168	$931.22	$931.20	$931.20