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	$247.95	13.289%	$280.9001	$280.90	$280.90	$280.90
Purchase #2	$6.79	9.312%	$7.4223	$7.42	$7.40	$7.40
Purchase #3	$184.43	8.283%	$199.7063	$199.71	$199.70	$199.70
Purchase #4	$143.30	11.375%	$159.6004	$159.60	$159.60	$159.60
Purchase #5	$210.35	4.260%	$219.3109	$219.31	$219.30	$219.30
Purchase #6	$192.43	13.632%	$218.6621	$218.66	$218.65	$218.70
Purchase #7	$54.34	12.574%	$61.1727	$61.17	$61.15	$61.20
7 purchase totals =	$1,039.59		$1,146.7748	$1,146.77	$1,146.70	$1,146.80