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	$201.40	5.161%	$211.7943	$211.79	$211.80	$211.80
Purchase #2	$87.30	5.729%	$92.3014	$92.30	$92.30	$92.30
Purchase #3	$106.67	13.331%	$120.8902	$120.89	$120.90	$120.90
Purchase #4	$40.68	10.759%	$45.0568	$45.06	$45.05	$45.10
Purchase #5	$75.95	12.660%	$85.5653	$85.57	$85.55	$85.60
Purchase #6	$145.75	13.525%	$165.4627	$165.46	$165.45	$165.50
Purchase #7	$166.35	13.532%	$188.8605	$188.86	$188.85	$188.90
7 purchase totals =	$824.10		$909.9312	$909.93	$909.90	$910.10