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	$60.30	11.763%	$67.3931	$67.39	$67.40	$67.40
Purchase #2	$13.54	11.630%	$15.1147	$15.11	$15.10	$15.10
Purchase #3	$191.84	6.571%	$204.4458	$204.45	$204.45	$204.40
Purchase #4	$167.78	7.191%	$179.8451	$179.85	$179.85	$179.80
Purchase #5	$170.57	11.802%	$190.7007	$190.70	$190.70	$190.70
Purchase #6	$146.85	12.573%	$165.3135	$165.31	$165.30	$165.30
Purchase #7	$213.45	5.662%	$225.5355	$225.54	$225.55	$225.50
7 purchase totals =	$964.33		$1,048.3484	$1,048.35	$1,048.35	$1,048.20