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	$214.25	13.353%	$242.8588	$242.86	$242.85	$242.90
Purchase #2	$125.40	10.174%	$138.1582	$138.16	$138.15	$138.20
Purchase #3	$167.25	13.692%	$190.1499	$190.15	$190.15	$190.10
Purchase #4	$198.70	7.457%	$213.5171	$213.52	$213.50	$213.50
Purchase #5	$33.33	13.386%	$37.7916	$37.79	$37.80	$37.80
Purchase #6	$76.43	11.429%	$85.1652	$85.17	$85.15	$85.20
Purchase #7	$231.78	9.260%	$253.2428	$253.24	$253.25	$253.20
7 purchase totals =	$1,047.14		$1,160.8836	$1,160.89	$1,160.85	$1,160.90