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	$132.67	9.218%	$144.8995	$144.90	$144.90	$144.90
Purchase #2	$113.58	8.458%	$123.1866	$123.19	$123.20	$123.20
Purchase #3	$221.79	5.165%	$233.2455	$233.25	$233.25	$233.20
Purchase #4	$74.46	11.324%	$82.8919	$82.89	$82.90	$82.90
Purchase #5	$241.65	7.555%	$259.9067	$259.91	$259.90	$259.90
Purchase #6	$53.42	8.664%	$58.0483	$58.05	$58.05	$58.00
Purchase #7	$235.75	12.201%	$264.5139	$264.51	$264.50	$264.50
7 purchase totals =	$1,073.32		$1,166.6924	$1,166.70	$1,166.70	$1,166.60