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	$14.88	5.765%	$15.7378	$15.74	$15.75	$15.70
Purchase #2	$195.72	13.228%	$221.6098	$221.61	$221.60	$221.60
Purchase #3	$24.96	11.414%	$27.8089	$27.81	$27.80	$27.80
Purchase #4	$198.52	13.439%	$225.1991	$225.20	$225.20	$225.20
Purchase #5	$76.92	11.512%	$85.775	$85.78	$85.80	$85.80
Purchase #6	$54.91	11.185%	$61.0517	$61.05	$61.05	$61.10
Purchase #7	$60.46	11.778%	$67.581	$67.58	$67.60	$67.60
7 purchase totals =	$626.37		$704.7633	$704.77	$704.80	$704.80