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	$150.50	4.653%	$157.5028	$157.50	$157.50	$157.50
Purchase #2	$152.48	9.618%	$167.1455	$167.15	$167.15	$167.10
Purchase #3	$170.76	11.714%	$190.7628	$190.76	$190.75	$190.80
Purchase #4	$126.96	12.766%	$143.1677	$143.17	$143.15	$143.20
Purchase #5	$150.82	5.272%	$158.7712	$158.77	$158.75	$158.80
Purchase #6	$103.30	4.642%	$108.0952	$108.10	$108.10	$108.10
Purchase #7	$16.68	13.645%	$18.956	$18.96	$18.95	$19.00
7 purchase totals =	$871.50		$944.4012	$944.41	$944.35	$944.50