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	$227.70	4.813%	$238.6592	$238.66	$238.65	$238.70
Purchase #2	$215.70	11.417%	$240.3265	$240.33	$240.35	$240.30
Purchase #3	$222.81	9.427%	$243.8143	$243.81	$243.80	$243.80
Purchase #4	$158.93	10.495%	$175.6097	$175.61	$175.60	$175.60
Purchase #5	$126.77	11.178%	$140.9404	$140.94	$140.95	$140.90
Purchase #6	$177.63	4.291%	$185.2521	$185.25	$185.25	$185.30
Purchase #7	$28.70	12.285%	$32.2258	$32.23	$32.25	$32.20
7 purchase totals =	$1,158.24		$1,256.8280	$1,256.83	$1,256.85	$1,256.80