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	$169.65	5.105%	$178.3106	$178.31	$178.30	$178.30
Purchase #2	$33.69	11.219%	$37.4697	$37.47	$37.45	$37.50
Purchase #3	$141.68	8.804%	$154.1535	$154.15	$154.15	$154.20
Purchase #4	$45.66	12.717%	$51.4666	$51.47	$51.45	$51.50
Purchase #5	$90.53	11.718%	$101.1383	$101.14	$101.15	$101.10
Purchase #6	$151.75	3.203%	$156.6106	$156.61	$156.60	$156.60
Purchase #7	$248.31	10.593%	$274.6135	$274.61	$274.60	$274.60
7 purchase totals =	$881.27		$953.7628	$953.76	$953.70	$953.80