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	$167.58	11.853%	$187.4433	$187.44	$187.45	$187.40
Purchase #2	$101.53	3.762%	$105.3496	$105.35	$105.35	$105.30
Purchase #3	$55.32	8.277%	$59.8988	$59.90	$59.90	$59.90
Purchase #4	$242.60	7.429%	$260.6228	$260.62	$260.60	$260.60
Purchase #5	$15.77	13.157%	$17.8449	$17.84	$17.85	$17.80
Purchase #6	$7.45	11.710%	$8.3224	$8.32	$8.30	$8.30
Purchase #7	$200.90	7.769%	$216.5079	$216.51	$216.50	$216.50
7 purchase totals =	$791.15		$855.9897	$855.98	$855.95	$855.80