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	$41.50	10.471%	$45.8455	$45.85	$45.85	$45.80
Purchase #2	$84.80	3.824%	$88.0428	$88.04	$88.05	$88.00
Purchase #3	$240.55	6.719%	$256.7126	$256.71	$256.70	$256.70
Purchase #4	$92.60	8.386%	$100.3654	$100.37	$100.35	$100.40
Purchase #5	$91.71	8.369%	$99.3852	$99.39	$99.40	$99.40
Purchase #6	$221.81	7.628%	$238.7297	$238.73	$238.75	$238.70
Purchase #7	$43.90	10.639%	$48.5705	$48.57	$48.55	$48.60
7 purchase totals =	$816.87		$877.6517	$877.66	$877.65	$877.60