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	$132.79	3.397%	$137.3009	$137.30	$137.30	$137.30
Purchase #2	$208.51	3.733%	$216.2937	$216.29	$216.30	$216.30
Purchase #3	$176.79	13.863%	$201.2984	$201.30	$201.30	$201.30
Purchase #4	$63.34	4.135%	$65.9591	$65.96	$65.95	$66.00
Purchase #5	$98.98	12.842%	$111.691	$111.69	$111.70	$111.70
Purchase #6	$166.27	11.504%	$185.3977	$185.40	$185.40	$185.40
Purchase #7	$221.98	4.687%	$232.3842	$232.38	$232.40	$232.40
7 purchase totals =	$1,068.66		$1,150.3250	$1,150.32	$1,150.35	$1,150.40