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	$82.31	7.787%	$88.7195	$88.72	$88.70	$88.70
Purchase #2	$130.90	7.727%	$141.0146	$141.01	$141.00	$141.00
Purchase #3	$231.61	7.408%	$248.7677	$248.77	$248.75	$248.80
Purchase #4	$154.45	11.364%	$172.0017	$172.00	$172.00	$172.00
Purchase #5	$101.68	9.824%	$111.669	$111.67	$111.65	$111.70
Purchase #6	$196.78	10.645%	$217.7272	$217.73	$217.75	$217.70
Purchase #7	$47.47	12.431%	$53.371	$53.37	$53.35	$53.40
7 purchase totals =	$945.20		$1,033.2707	$1,033.27	$1,033.20	$1,033.30