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	$213.86	4.147%	$222.7288	$222.73	$222.75	$222.70
Purchase #2	$227.32	5.730%	$240.3454	$240.35	$240.35	$240.30
Purchase #3	$122.83	4.126%	$127.898	$127.90	$127.90	$127.90
Purchase #4	$178.90	7.411%	$192.1583	$192.16	$192.15	$192.20
Purchase #5	$235.54	12.578%	$265.1662	$265.17	$265.15	$265.20
Purchase #6	$144.89	5.511%	$152.8749	$152.87	$152.85	$152.90
Purchase #7	$98.32	8.536%	$106.7126	$106.71	$106.70	$106.70
7 purchase totals =	$1,221.66		$1,307.8842	$1,307.89	$1,307.85	$1,307.90