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	$195.59	6.690%	$208.675	$208.68	$208.70	$208.70
Purchase #2	$42.90	13.141%	$48.5375	$48.54	$48.55	$48.50
Purchase #3	$118.31	11.313%	$131.6944	$131.69	$131.70	$131.70
Purchase #4	$48.63	11.803%	$54.3698	$54.37	$54.35	$54.40
Purchase #5	$160.26	13.723%	$182.2525	$182.25	$182.25	$182.30
Purchase #6	$100.27	11.849%	$112.151	$112.15	$112.15	$112.20
Purchase #7	$199.98	6.744%	$213.4667	$213.47	$213.45	$213.50
7 purchase totals =	$865.94		$951.1469	$951.15	$951.15	$951.30