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	$237.44	13.523%	$269.549	$269.55	$269.55	$269.50
Purchase #2	$149.89	13.337%	$169.8808	$169.88	$169.90	$169.90
Purchase #3	$33.28	10.873%	$36.8985	$36.90	$36.90	$36.90
Purchase #4	$76.99	8.457%	$83.501	$83.50	$83.50	$83.50
Purchase #5	$172.72	7.283%	$185.2992	$185.30	$185.30	$185.30
Purchase #6	$226.63	3.142%	$233.7507	$233.75	$233.75	$233.80
Purchase #7	$36.57	7.231%	$39.2144	$39.21	$39.20	$39.20
7 purchase totals =	$933.52		$1,018.0936	$1,018.09	$1,018.10	$1,018.10