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	$35.92	3.134%	$37.0457	$37.05	$37.05	$37.00
Purchase #2	$32.64	10.459%	$36.0538	$36.05	$36.05	$36.10
Purchase #3	$127.57	13.470%	$144.7537	$144.75	$144.75	$144.80
Purchase #4	$49.42	5.356%	$52.0669	$52.07	$52.05	$52.10
Purchase #5	$234.52	9.497%	$256.7924	$256.79	$256.80	$256.80
Purchase #6	$131.61	4.788%	$137.9115	$137.91	$137.90	$137.90
Purchase #7	$6.89	9.200%	$7.5239	$7.52	$7.50	$7.50
7 purchase totals =	$618.57		$672.1479	$672.14	$672.10	$672.20