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	$152.83	13.596%	$173.6088	$173.61	$173.60	$173.60
Purchase #2	$214.41	3.619%	$222.1695	$222.17	$222.15	$222.20
Purchase #3	$226.29	10.709%	$250.5234	$250.52	$250.50	$250.50
Purchase #4	$12.90	9.546%	$14.1314	$14.13	$14.15	$14.10
Purchase #5	$216.53	3.827%	$224.8166	$224.82	$224.80	$224.80
Purchase #6	$90.59	10.223%	$99.851	$99.85	$99.85	$99.90
Purchase #7	$133.36	11.134%	$148.2083	$148.21	$148.20	$148.20
7 purchase totals =	$1,046.91		$1,133.3090	$1,133.31	$1,133.25	$1,133.30