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	$131.44	12.801%	$148.2656	$148.27	$148.25	$148.30
Purchase #2	$35.76	12.820%	$40.3444	$40.34	$40.35	$40.30
Purchase #3	$78.74	12.197%	$88.3439	$88.34	$88.35	$88.30
Purchase #4	$208.51	10.227%	$229.8343	$229.83	$229.85	$229.80
Purchase #5	$221.79	3.200%	$228.8873	$228.89	$228.90	$228.90
Purchase #6	$78.92	4.558%	$82.5172	$82.52	$82.50	$82.50
Purchase #7	$136.70	8.680%	$148.5656	$148.57	$148.55	$148.60
7 purchase totals =	$891.86		$966.7583	$966.76	$966.75	$966.70