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	$70.31	9.612%	$77.0682	$77.07	$77.05	$77.10
Purchase #2	$74.89	4.454%	$78.2256	$78.23	$78.25	$78.20
Purchase #3	$53.76	8.733%	$58.4549	$58.45	$58.45	$58.50
Purchase #4	$154.61	10.359%	$170.626	$170.63	$170.65	$170.60
Purchase #5	$39.94	7.599%	$42.975	$42.98	$43.00	$43.00
Purchase #6	$172.35	8.640%	$187.241	$187.24	$187.25	$187.20
Purchase #7	$60.38	4.158%	$62.8906	$62.89	$62.90	$62.90
7 purchase totals =	$626.24		$677.4813	$677.49	$677.55	$677.50