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	$37.68	12.667%	$42.4529	$42.45	$42.45	$42.50
Purchase #2	$157.82	4.317%	$164.6331	$164.63	$164.65	$164.60
Purchase #3	$174.48	12.250%	$195.8538	$195.85	$195.85	$195.90
Purchase #4	$126.37	11.267%	$140.6081	$140.61	$140.60	$140.60
Purchase #5	$164.85	3.728%	$170.9956	$171.00	$171.00	$171.00
Purchase #6	$151.97	8.549%	$164.9619	$164.96	$164.95	$165.00
Purchase #7	$15.40	4.578%	$16.105	$16.11	$16.10	$16.10
7 purchase totals =	$828.57		$895.6104	$895.61	$895.60	$895.70