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	$226.75	9.206%	$247.6246	$247.62	$247.60	$247.60
Purchase #2	$98.57	11.471%	$109.877	$109.88	$109.90	$109.90
Purchase #3	$10.47	11.161%	$11.6386	$11.64	$11.65	$11.60
Purchase #4	$59.85	12.325%	$67.2265	$67.23	$67.25	$67.20
Purchase #5	$66.74	8.750%	$72.5798	$72.58	$72.60	$72.60
Purchase #6	$101.66	10.835%	$112.6749	$112.67	$112.65	$112.70
Purchase #7	$12.28	10.246%	$13.5382	$13.54	$13.55	$13.50
7 purchase totals =	$576.32		$635.1596	$635.16	$635.20	$635.10