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	$180.27	8.670%	$195.8994	$195.90	$195.90	$195.90
Purchase #2	$60.48	9.780%	$66.3949	$66.39	$66.40	$66.40
Purchase #3	$75.70	3.637%	$78.4532	$78.45	$78.45	$78.50
Purchase #4	$92.42	3.115%	$95.2989	$95.30	$95.30	$95.30
Purchase #5	$151.54	9.780%	$166.3606	$166.36	$166.35	$166.40
Purchase #6	$138.40	8.460%	$150.1086	$150.11	$150.10	$150.10
Purchase #7	$49.96	4.134%	$52.0253	$52.03	$52.05	$52.00
7 purchase totals =	$748.77		$804.5409	$804.54	$804.55	$804.60