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	$245.33	4.216%	$255.6731	$255.67	$255.65	$255.70
Purchase #2	$38.62	4.858%	$40.4962	$40.50	$40.50	$40.50
Purchase #3	$204.39	10.490%	$225.8305	$225.83	$225.85	$225.80
Purchase #4	$196.28	4.588%	$205.2853	$205.29	$205.30	$205.30
Purchase #5	$62.68	6.390%	$66.6853	$66.69	$66.70	$66.70
Purchase #6	$115.81	11.858%	$129.5427	$129.54	$129.55	$129.50
Purchase #7	$93.90	11.494%	$104.6929	$104.69	$104.70	$104.70
7 purchase totals =	$957.01		$1,028.2060	$1,028.21	$1,028.25	$1,028.20