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	$134.48	5.561%	$141.9584	$141.96	$141.95	$142.00
Purchase #2	$16.88	7.594%	$18.1619	$18.16	$18.15	$18.20
Purchase #3	$137.79	8.231%	$149.1315	$149.13	$149.15	$149.10
Purchase #4	$73.89	13.489%	$83.857	$83.86	$83.85	$83.90
Purchase #5	$196.90	3.112%	$203.0275	$203.03	$203.05	$203.00
Purchase #6	$161.58	11.333%	$179.8919	$179.89	$179.90	$179.90
Purchase #7	$50.72	13.384%	$57.5084	$57.51	$57.50	$57.50
7 purchase totals =	$772.24		$833.5366	$833.54	$833.55	$833.60