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	$107.72	9.137%	$117.5624	$117.56	$117.55	$117.60
Purchase #2	$32.98	13.119%	$37.3066	$37.31	$37.30	$37.30
Purchase #3	$172.55	9.238%	$188.4902	$188.49	$188.50	$188.50
Purchase #4	$179.82	10.713%	$199.0841	$199.08	$199.10	$199.10
Purchase #5	$62.27	4.394%	$65.0061	$65.01	$65.00	$65.00
Purchase #6	$28.25	3.733%	$29.3046	$29.30	$29.30	$29.30
Purchase #7	$120.95	10.423%	$133.5566	$133.56	$133.55	$133.60
7 purchase totals =	$704.54		$770.3106	$770.31	$770.30	$770.40