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	$127.28	11.137%	$141.4552	$141.46	$141.45	$141.50
Purchase #2	$50.56	12.324%	$56.791	$56.79	$56.80	$56.80
Purchase #3	$242.86	8.686%	$263.9548	$263.95	$263.95	$264.00
Purchase #4	$146.46	5.110%	$153.9441	$153.94	$153.95	$153.90
Purchase #5	$221.37	10.401%	$244.3947	$244.39	$244.40	$244.40
Purchase #6	$125.93	13.157%	$142.4986	$142.50	$142.50	$142.50
Purchase #7	$117.89	6.485%	$125.5352	$125.54	$125.55	$125.50
7 purchase totals =	$1,032.35		$1,128.5736	$1,128.57	$1,128.60	$1,128.60