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	$9.81	5.502%	$10.3497	$10.35	$10.35	$10.30
Purchase #2	$123.30	8.248%	$133.4698	$133.47	$133.45	$133.50
Purchase #3	$122.98	11.805%	$137.4978	$137.50	$137.50	$137.50
Purchase #4	$243.83	7.687%	$262.5732	$262.57	$262.55	$262.60
Purchase #5	$71.65	9.465%	$78.4317	$78.43	$78.45	$78.40
Purchase #6	$248.58	9.321%	$271.7501	$271.75	$271.75	$271.80
Purchase #7	$119.25	7.634%	$128.3535	$128.35	$128.35	$128.40
7 purchase totals =	$939.40		$1,022.4258	$1,022.42	$1,022.40	$1,022.50