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	$231.69	11.525%	$258.3923	$258.39	$258.40	$258.40
Purchase #2	$88.35	6.850%	$94.402	$94.40	$94.40	$94.40
Purchase #3	$70.78	11.139%	$78.6642	$78.66	$78.65	$78.70
Purchase #4	$26.40	8.139%	$28.5487	$28.55	$28.55	$28.50
Purchase #5	$196.58	8.564%	$213.4151	$213.42	$213.40	$213.40
Purchase #6	$175.59	13.637%	$199.5352	$199.54	$199.55	$199.50
Purchase #7	$134.69	10.739%	$149.1544	$149.15	$149.15	$149.20
7 purchase totals =	$924.08		$1,022.1119	$1,022.11	$1,022.10	$1,022.10