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	$112.29	6.628%	$119.7326	$119.73	$119.75	$119.70
Purchase #2	$244.86	7.185%	$262.4532	$262.45	$262.45	$262.50
Purchase #3	$105.75	7.358%	$113.5311	$113.53	$113.55	$113.50
Purchase #4	$91.56	8.461%	$99.3069	$99.31	$99.30	$99.30
Purchase #5	$71.31	8.719%	$77.5275	$77.53	$77.55	$77.50
Purchase #6	$125.37	12.431%	$140.9547	$140.95	$140.95	$141.00
Purchase #7	$110.61	11.265%	$123.0702	$123.07	$123.05	$123.10
7 purchase totals =	$861.75		$936.5762	$936.57	$936.60	$936.60