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	$235.90	8.184%	$255.2061	$255.21	$255.20	$255.20
Purchase #2	$133.85	7.267%	$143.5769	$143.58	$143.60	$143.60
Purchase #3	$203.44	5.759%	$215.1561	$215.16	$215.15	$215.20
Purchase #4	$8.58	8.495%	$9.3089	$9.31	$9.30	$9.30
Purchase #5	$185.77	6.802%	$198.4061	$198.41	$198.40	$198.40
Purchase #6	$230.70	5.557%	$243.52	$243.52	$243.50	$243.50
Purchase #7	$69.67	12.463%	$78.353	$78.35	$78.35	$78.40
7 purchase totals =	$1,067.91		$1,143.5271	$1,143.54	$1,143.50	$1,143.60