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	$65.81	11.695%	$73.5065	$73.51	$73.50	$73.50
Purchase #2	$150.97	11.630%	$168.5278	$168.53	$168.55	$168.50
Purchase #3	$57.62	7.761%	$62.0919	$62.09	$62.10	$62.10
Purchase #4	$233.91	5.638%	$247.0978	$247.10	$247.10	$247.10
Purchase #5	$125.67	11.221%	$139.7714	$139.77	$139.75	$139.80
Purchase #6	$139.88	4.476%	$146.141	$146.14	$146.15	$146.10
Purchase #7	$16.54	9.342%	$18.0852	$18.09	$18.10	$18.10
7 purchase totals =	$790.40		$855.2216	$855.23	$855.25	$855.20