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	$17.60	5.316%	$18.5356	$18.54	$18.55	$18.50
Purchase #2	$173.29	13.198%	$196.1608	$196.16	$196.15	$196.20
Purchase #3	$40.72	5.328%	$42.8896	$42.89	$42.90	$42.90
Purchase #4	$28.59	5.188%	$30.0732	$30.07	$30.05	$30.10
Purchase #5	$55.98	7.435%	$60.1421	$60.14	$60.15	$60.10
Purchase #6	$46.71	6.141%	$49.5785	$49.58	$49.60	$49.60
Purchase #7	$60.95	10.548%	$67.379	$67.38	$67.40	$67.40
7 purchase totals =	$423.84		$464.7588	$464.76	$464.80	$464.80