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	$131.80	8.861%	$143.4788	$143.48	$143.50	$143.50
Purchase #2	$65.82	7.173%	$70.5413	$70.54	$70.55	$70.50
Purchase #3	$187.44	8.684%	$203.7173	$203.72	$203.70	$203.70
Purchase #4	$116.61	3.154%	$120.2879	$120.29	$120.30	$120.30
Purchase #5	$91.98	13.390%	$104.2961	$104.30	$104.30	$104.30
Purchase #6	$185.81	5.549%	$196.1206	$196.12	$196.10	$196.10
Purchase #7	$120.94	4.313%	$126.1561	$126.16	$126.15	$126.20
7 purchase totals =	$900.40		$964.5981	$964.61	$964.60	$964.60