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	$222.46	7.231%	$238.5461	$238.55	$238.55	$238.50
Purchase #2	$103.33	7.445%	$111.0229	$111.02	$111.00	$111.00
Purchase #3	$223.81	13.114%	$253.1604	$253.16	$253.15	$253.20
Purchase #4	$67.64	3.657%	$70.1136	$70.11	$70.10	$70.10
Purchase #5	$13.43	4.544%	$14.0403	$14.04	$14.05	$14.00
Purchase #6	$61.70	7.742%	$66.4768	$66.48	$66.50	$66.50
Purchase #7	$24.93	10.336%	$27.5068	$27.51	$27.50	$27.50
7 purchase totals =	$717.30		$780.8669	$780.87	$780.85	$780.80