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	$183.39	4.795%	$192.1836	$192.18	$192.20	$192.20
Purchase #2	$118.72	8.253%	$128.518	$128.52	$128.50	$128.50
Purchase #3	$49.28	3.780%	$51.1428	$51.14	$51.15	$51.10
Purchase #4	$73.71	3.230%	$76.0908	$76.09	$76.10	$76.10
Purchase #5	$222.56	7.345%	$238.907	$238.91	$238.90	$238.90
Purchase #6	$247.46	11.688%	$276.3831	$276.38	$276.40	$276.40
Purchase #7	$122.90	12.188%	$137.8791	$137.88	$137.90	$137.90
7 purchase totals =	$1,018.02		$1,101.1044	$1,101.10	$1,101.15	$1,101.10