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	$154.73	11.236%	$172.1155	$172.12	$172.10	$172.10
Purchase #2	$67.80	6.411%	$72.1467	$72.15	$72.15	$72.10
Purchase #3	$49.28	11.182%	$54.7905	$54.79	$54.80	$54.80
Purchase #4	$238.94	7.337%	$256.471	$256.47	$256.45	$256.50
Purchase #5	$85.48	12.193%	$95.9026	$95.90	$95.90	$95.90
Purchase #6	$171.84	6.180%	$182.4597	$182.46	$182.45	$182.50
Purchase #7	$53.94	9.213%	$58.9095	$58.91	$58.90	$58.90
7 purchase totals =	$822.01		$892.7955	$892.80	$892.75	$892.80