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	$236.34	4.441%	$246.8359	$246.84	$246.85	$246.80
Purchase #2	$216.65	4.127%	$225.5911	$225.59	$225.60	$225.60
Purchase #3	$238.78	6.173%	$253.5199	$253.52	$253.50	$253.50
Purchase #4	$222.82	8.834%	$242.5039	$242.50	$242.50	$242.50
Purchase #5	$101.49	5.321%	$106.8903	$106.89	$106.90	$106.90
Purchase #6	$44.83	11.527%	$49.9976	$50.00	$50.00	$50.00
Purchase #7	$56.56	5.414%	$59.6222	$59.62	$59.60	$59.60
7 purchase totals =	$1,117.47		$1,184.9609	$1,184.96	$1,184.95	$1,184.90