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	$100.51	3.856%	$104.3857	$104.39	$104.40	$104.40
Purchase #2	$106.37	4.767%	$111.4407	$111.44	$111.45	$111.40
Purchase #3	$40.70	12.245%	$45.6837	$45.68	$45.70	$45.70
Purchase #4	$102.43	13.625%	$116.3861	$116.39	$116.40	$116.40
Purchase #5	$242.73	4.823%	$254.4369	$254.44	$254.45	$254.40
Purchase #6	$111.45	7.815%	$120.1598	$120.16	$120.15	$120.20
Purchase #7	$219.61	4.278%	$229.0049	$229.00	$229.00	$229.00
7 purchase totals =	$923.80		$981.4978	$981.50	$981.55	$981.50