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	$226.46	13.766%	$257.6345	$257.63	$257.65	$257.60
Purchase #2	$121.41	12.368%	$136.426	$136.43	$136.45	$136.40
Purchase #3	$90.35	11.359%	$100.6129	$100.61	$100.60	$100.60
Purchase #4	$70.40	5.550%	$74.3072	$74.31	$74.30	$74.30
Purchase #5	$149.40	4.638%	$156.3292	$156.33	$156.35	$156.30
Purchase #6	$219.61	11.166%	$244.1317	$244.13	$244.15	$244.10
Purchase #7	$35.90	5.643%	$37.9258	$37.93	$37.95	$37.90
7 purchase totals =	$913.53		$1,007.3673	$1,007.37	$1,007.45	$1,007.20