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	$183.95	6.300%	$195.5389	$195.54	$195.55	$195.50
Purchase #2	$139.35	6.848%	$148.8927	$148.89	$148.90	$148.90
Purchase #3	$43.59	11.200%	$48.4721	$48.47	$48.45	$48.50
Purchase #4	$209.77	11.497%	$233.8873	$233.89	$233.90	$233.90
Purchase #5	$100.62	13.568%	$114.2721	$114.27	$114.25	$114.30
Purchase #6	$32.57	11.158%	$36.2042	$36.20	$36.20	$36.20
Purchase #7	$143.31	6.310%	$152.3529	$152.35	$152.35	$152.40
7 purchase totals =	$853.16		$929.6202	$929.61	$929.60	$929.70