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	$147.40	3.319%	$152.2922	$152.29	$152.30	$152.30
Purchase #2	$124.58	13.171%	$140.9884	$140.99	$141.00	$141.00
Purchase #3	$180.35	10.818%	$199.8603	$199.86	$199.85	$199.90
Purchase #4	$209.43	13.395%	$237.4831	$237.48	$237.50	$237.50
Purchase #5	$49.66	10.455%	$54.852	$54.85	$54.85	$54.90
Purchase #6	$101.37	6.800%	$108.2632	$108.26	$108.25	$108.30
Purchase #7	$215.83	6.451%	$229.7532	$229.75	$229.75	$229.80
7 purchase totals =	$1,028.62		$1,123.4924	$1,123.48	$1,123.50	$1,123.70