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	$145.68	10.330%	$160.7287	$160.73	$160.75	$160.70
Purchase #2	$156.63	8.358%	$169.7211	$169.72	$169.70	$169.70
Purchase #3	$167.70	12.201%	$188.1611	$188.16	$188.15	$188.20
Purchase #4	$55.50	4.329%	$57.9026	$57.90	$57.90	$57.90
Purchase #5	$109.85	13.296%	$124.4557	$124.46	$124.45	$124.50
Purchase #6	$172.91	3.803%	$179.4858	$179.49	$179.50	$179.50
Purchase #7	$162.56	6.500%	$173.1264	$173.13	$173.15	$173.10
7 purchase totals =	$970.83		$1,053.5814	$1,053.59	$1,053.60	$1,053.60