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	$123.78	6.333%	$131.619	$131.62	$131.60	$131.60
Purchase #2	$199.55	5.134%	$209.7949	$209.79	$209.80	$209.80
Purchase #3	$57.57	9.736%	$63.175	$63.18	$63.20	$63.20
Purchase #4	$103.47	7.843%	$111.5852	$111.59	$111.60	$111.60
Purchase #5	$176.43	9.307%	$192.8503	$192.85	$192.85	$192.90
Purchase #6	$235.91	7.596%	$253.8297	$253.83	$253.85	$253.80
Purchase #7	$184.34	7.165%	$197.548	$197.55	$197.55	$197.50
7 purchase totals =	$1,081.05		$1,160.4021	$1,160.41	$1,160.45	$1,160.40