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	$42.65	4.843%	$44.7155	$44.72	$44.70	$44.70
Purchase #2	$234.68	8.688%	$255.069	$255.07	$255.05	$255.10
Purchase #3	$222.91	9.861%	$244.8912	$244.89	$244.90	$244.90
Purchase #4	$14.41	9.653%	$15.801	$15.80	$15.80	$15.80
Purchase #5	$36.71	9.706%	$40.2731	$40.27	$40.25	$40.30
Purchase #6	$155.99	10.157%	$171.8339	$171.83	$171.85	$171.80
Purchase #7	$67.94	5.253%	$71.5089	$71.51	$71.50	$71.50
7 purchase totals =	$775.29		$844.0926	$844.09	$844.05	$844.10