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	$128.75	9.532%	$141.0225	$141.02	$141.00	$141.00
Purchase #2	$248.94	12.480%	$280.0077	$280.01	$280.00	$280.00
Purchase #3	$206.93	11.346%	$230.4083	$230.41	$230.40	$230.40
Purchase #4	$118.86	8.117%	$128.5079	$128.51	$128.50	$128.50
Purchase #5	$66.29	9.541%	$72.6147	$72.61	$72.60	$72.60
Purchase #6	$173.66	6.791%	$185.4533	$185.45	$185.45	$185.50
Purchase #7	$86.68	9.113%	$94.5791	$94.58	$94.60	$94.60
7 purchase totals =	$1,030.11		$1,132.5935	$1,132.59	$1,132.55	$1,132.60