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	$132.40	10.828%	$146.7363	$146.74	$146.75	$146.70
Purchase #2	$190.63	8.754%	$207.3178	$207.32	$207.30	$207.30
Purchase #3	$54.66	8.564%	$59.3411	$59.34	$59.35	$59.30
Purchase #4	$121.90	7.377%	$130.8926	$130.89	$130.90	$130.90
Purchase #5	$106.52	10.683%	$117.8995	$117.90	$117.90	$117.90
Purchase #6	$20.27	5.455%	$21.3757	$21.38	$21.40	$21.40
Purchase #7	$39.87	5.512%	$42.0676	$42.07	$42.05	$42.10
7 purchase totals =	$666.25		$725.6306	$725.64	$725.65	$725.60