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	$84.77	6.782%	$90.5191	$90.52	$90.50	$90.50
Purchase #2	$145.45	6.831%	$155.3857	$155.39	$155.40	$155.40
Purchase #3	$110.82	12.313%	$124.4653	$124.47	$124.45	$124.50
Purchase #4	$164.25	7.704%	$176.9038	$176.90	$176.90	$176.90
Purchase #5	$57.89	6.549%	$61.6812	$61.68	$61.70	$61.70
Purchase #6	$134.54	5.198%	$141.5334	$141.53	$141.55	$141.50
Purchase #7	$71.60	3.809%	$74.3272	$74.33	$74.35	$74.30
7 purchase totals =	$769.32		$824.8157	$824.82	$824.85	$824.80