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	$144.74	5.388%	$152.5386	$152.54	$152.55	$152.50
Purchase #2	$72.99	10.788%	$80.8642	$80.86	$80.85	$80.90
Purchase #3	$250.30	5.257%	$263.4583	$263.46	$263.45	$263.50
Purchase #4	$104.31	12.653%	$117.5083	$117.51	$117.50	$117.50
Purchase #5	$104.43	8.850%	$113.6721	$113.67	$113.65	$113.70
Purchase #6	$50.54	3.171%	$52.1426	$52.14	$52.15	$52.10
Purchase #7	$229.87	13.432%	$260.7461	$260.75	$260.75	$260.70
7 purchase totals =	$957.18		$1,040.9302	$1,040.93	$1,040.90	$1,040.90