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	$190.89	6.616%	$203.5193	$203.52	$203.50	$203.50
Purchase #2	$225.36	7.171%	$241.5206	$241.52	$241.50	$241.50
Purchase #3	$36.88	3.823%	$38.2899	$38.29	$38.30	$38.30
Purchase #4	$106.52	4.300%	$111.1004	$111.10	$111.10	$111.10
Purchase #5	$201.54	13.708%	$229.1671	$229.17	$229.15	$229.20
Purchase #6	$122.81	12.795%	$138.5235	$138.52	$138.50	$138.50
Purchase #7	$243.57	11.295%	$271.0812	$271.08	$271.10	$271.10
7 purchase totals =	$1,127.57		$1,233.2020	$1,233.20	$1,233.15	$1,233.20