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	$53.78	12.556%	$60.5326	$60.53	$60.55	$60.50
Purchase #2	$168.59	13.270%	$190.9619	$190.96	$190.95	$191.00
Purchase #3	$140.85	6.601%	$150.1475	$150.15	$150.15	$150.10
Purchase #4	$213.38	4.116%	$222.1627	$222.16	$222.15	$222.20
Purchase #5	$35.81	12.647%	$40.3389	$40.34	$40.35	$40.30
Purchase #6	$135.47	6.145%	$143.7946	$143.79	$143.80	$143.80
Purchase #7	$178.74	8.248%	$193.4825	$193.48	$193.50	$193.50
7 purchase totals =	$926.62		$1,001.4207	$1,001.41	$1,001.45	$1,001.40