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	$60.78	3.182%	$62.714	$62.71	$62.70	$62.70
Purchase #2	$123.84	9.251%	$135.2964	$135.30	$135.30	$135.30
Purchase #3	$105.58	5.321%	$111.1979	$111.20	$111.20	$111.20
Purchase #4	$244.55	12.390%	$274.8497	$274.85	$274.85	$274.80
Purchase #5	$66.31	10.854%	$73.5073	$73.51	$73.50	$73.50
Purchase #6	$172.43	10.428%	$190.411	$190.41	$190.40	$190.40
Purchase #7	$245.36	6.124%	$260.3858	$260.39	$260.40	$260.40
7 purchase totals =	$1,018.85		$1,108.3621	$1,108.37	$1,108.35	$1,108.30