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	$22.50	7.140%	$24.1065	$24.11	$24.10	$24.10
Purchase #2	$164.42	5.281%	$173.103	$173.10	$173.10	$173.10
Purchase #3	$235.47	10.476%	$260.1378	$260.14	$260.15	$260.10
Purchase #4	$85.29	8.535%	$92.5695	$92.57	$92.55	$92.60
Purchase #5	$141.91	10.331%	$156.5707	$156.57	$156.55	$156.60
Purchase #6	$67.44	6.567%	$71.8688	$71.87	$71.85	$71.90
Purchase #7	$185.90	7.661%	$200.1418	$200.14	$200.15	$200.10
7 purchase totals =	$902.93		$978.4981	$978.50	$978.45	$978.50