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	$46.95	4.772%	$49.1905	$49.19	$49.20	$49.20
Purchase #2	$166.77	11.298%	$185.6117	$185.61	$185.60	$185.60
Purchase #3	$244.45	4.794%	$256.1689	$256.17	$256.15	$256.20
Purchase #4	$148.51	12.111%	$166.496	$166.50	$166.50	$166.50
Purchase #5	$59.78	12.555%	$67.2854	$67.29	$67.30	$67.30
Purchase #6	$248.49	6.692%	$265.119	$265.12	$265.10	$265.10
Purchase #7	$118.58	4.470%	$123.8805	$123.88	$123.90	$123.90
7 purchase totals =	$1,033.53		$1,113.7520	$1,113.76	$1,113.75	$1,113.80