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	$143.43	4.612%	$150.045	$150.05	$150.05	$150.00
Purchase #2	$68.38	13.553%	$77.6475	$77.65	$77.65	$77.60
Purchase #3	$31.75	5.671%	$33.5505	$33.55	$33.55	$33.60
Purchase #4	$52.92	12.447%	$59.507	$59.51	$59.50	$59.50
Purchase #5	$225.56	8.277%	$244.2296	$244.23	$244.25	$244.20
Purchase #6	$70.62	7.569%	$75.9652	$75.97	$75.95	$76.00
Purchase #7	$40.69	7.188%	$43.6148	$43.61	$43.60	$43.60
7 purchase totals =	$633.35		$684.5596	$684.57	$684.55	$684.50