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	$77.94	13.508%	$88.4681	$88.47	$88.45	$88.50
Purchase #2	$183.31	4.479%	$191.5205	$191.52	$191.50	$191.50
Purchase #3	$30.72	9.323%	$33.584	$33.58	$33.60	$33.60
Purchase #4	$42.33	6.468%	$45.0679	$45.07	$45.05	$45.10
Purchase #5	$175.76	8.821%	$191.2638	$191.26	$191.25	$191.30
Purchase #6	$153.33	7.861%	$165.3833	$165.38	$165.40	$165.40
Purchase #7	$205.69	3.726%	$213.354	$213.35	$213.35	$213.40
7 purchase totals =	$869.08		$928.6416	$928.63	$928.60	$928.80