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	$49.39	7.448%	$53.0686	$53.07	$53.05	$53.10
Purchase #2	$83.95	10.539%	$92.7975	$92.80	$92.80	$92.80
Purchase #3	$166.82	12.333%	$187.3939	$187.39	$187.40	$187.40
Purchase #4	$52.79	13.517%	$59.9256	$59.93	$59.95	$59.90
Purchase #5	$54.89	11.689%	$61.3061	$61.31	$61.30	$61.30
Purchase #6	$59.87	11.637%	$66.8371	$66.84	$66.85	$66.80
Purchase #7	$146.60	3.304%	$151.4437	$151.44	$151.45	$151.40
7 purchase totals =	$614.31		$672.7725	$672.78	$672.80	$672.70