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	$32.58	7.476%	$35.0157	$35.02	$35.00	$35.00
Purchase #2	$30.77	11.235%	$34.227	$34.23	$34.25	$34.20
Purchase #3	$80.55	12.310%	$90.4657	$90.47	$90.45	$90.50
Purchase #4	$133.31	5.145%	$140.1688	$140.17	$140.15	$140.20
Purchase #5	$246.96	13.445%	$280.1638	$280.16	$280.15	$280.20
Purchase #6	$224.42	11.479%	$250.1812	$250.18	$250.20	$250.20
Purchase #7	$227.71	10.348%	$251.2734	$251.27	$251.25	$251.30
7 purchase totals =	$976.30		$1,081.4956	$1,081.50	$1,081.45	$1,081.60