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	$177.72	7.132%	$190.395	$190.40	$190.40	$190.40
Purchase #2	$18.32	11.215%	$20.3746	$20.37	$20.35	$20.40
Purchase #3	$155.89	10.304%	$171.9529	$171.95	$171.95	$172.00
Purchase #4	$165.93	4.188%	$172.8791	$172.88	$172.90	$172.90
Purchase #5	$209.85	3.420%	$217.0269	$217.03	$217.05	$217.00
Purchase #6	$188.58	4.333%	$196.7512	$196.75	$196.75	$196.80
Purchase #7	$140.66	7.686%	$151.4711	$151.47	$151.45	$151.50
7 purchase totals =	$1,056.95		$1,120.8508	$1,120.85	$1,120.85	$1,121.00