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	$108.75	6.361%	$115.6676	$115.67	$115.65	$115.70
Purchase #2	$62.28	5.771%	$65.8742	$65.87	$65.85	$65.90
Purchase #3	$95.53	4.216%	$99.5575	$99.56	$99.55	$99.60
Purchase #4	$51.93	3.667%	$53.8343	$53.83	$53.85	$53.80
Purchase #5	$58.42	13.778%	$66.4691	$66.47	$66.45	$66.50
Purchase #6	$150.82	6.226%	$160.2101	$160.21	$160.20	$160.20
Purchase #7	$48.71	6.528%	$51.8898	$51.89	$51.90	$51.90
7 purchase totals =	$576.44		$613.5026	$613.50	$613.45	$613.60