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	$53.92	9.605%	$59.099	$59.10	$59.10	$59.10
Purchase #2	$84.51	6.584%	$90.0741	$90.07	$90.05	$90.10
Purchase #3	$155.84	6.864%	$166.5369	$166.54	$166.55	$166.50
Purchase #4	$64.57	10.700%	$71.479	$71.48	$71.50	$71.50
Purchase #5	$10.76	6.249%	$11.4324	$11.43	$11.45	$11.40
Purchase #6	$158.90	8.524%	$172.4446	$172.44	$172.45	$172.40
Purchase #7	$105.39	11.336%	$117.337	$117.34	$117.35	$117.30
7 purchase totals =	$633.89		$688.4030	$688.40	$688.45	$688.30