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	$81.40	11.436%	$90.7089	$90.71	$90.70	$90.70
Purchase #2	$171.61	11.505%	$191.3537	$191.35	$191.35	$191.40
Purchase #3	$239.79	4.652%	$250.945	$250.95	$250.95	$250.90
Purchase #4	$48.90	6.662%	$52.1577	$52.16	$52.15	$52.20
Purchase #5	$32.89	7.727%	$35.4314	$35.43	$35.45	$35.40
Purchase #6	$12.82	6.371%	$13.6368	$13.64	$13.65	$13.60
Purchase #7	$46.45	4.683%	$48.6253	$48.63	$48.65	$48.60
7 purchase totals =	$633.86		$682.8588	$682.87	$682.90	$682.80