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	$217.70	10.501%	$240.5607	$240.56	$240.55	$240.60
Purchase #2	$210.53	6.176%	$223.5323	$223.53	$223.55	$223.50
Purchase #3	$118.29	8.613%	$128.4783	$128.48	$128.50	$128.50
Purchase #4	$12.61	7.696%	$13.5805	$13.58	$13.60	$13.60
Purchase #5	$102.29	8.651%	$111.1391	$111.14	$111.15	$111.10
Purchase #6	$201.52	11.250%	$224.191	$224.19	$224.20	$224.20
Purchase #7	$119.72	13.235%	$135.5649	$135.56	$135.55	$135.60
7 purchase totals =	$982.66		$1,077.0468	$1,077.04	$1,077.10	$1,077.10