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	$231.65	10.874%	$256.8396	$256.84	$256.85	$256.80
Purchase #2	$75.46	7.697%	$81.2682	$81.27	$81.25	$81.30
Purchase #3	$156.57	9.424%	$171.3252	$171.33	$171.35	$171.30
Purchase #4	$104.85	11.196%	$116.589	$116.59	$116.60	$116.60
Purchase #5	$137.49	9.733%	$150.8719	$150.87	$150.85	$150.90
Purchase #6	$235.71	9.659%	$258.4772	$258.48	$258.50	$258.50
Purchase #7	$138.60	5.809%	$146.6513	$146.65	$146.65	$146.70
7 purchase totals =	$1,080.33		$1,182.0224	$1,182.03	$1,182.05	$1,182.10