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	$47.79	10.277%	$52.7014	$52.70	$52.70	$52.70
Purchase #2	$40.53	5.519%	$42.7669	$42.77	$42.75	$42.80
Purchase #3	$205.41	7.764%	$221.358	$221.36	$221.35	$221.40
Purchase #4	$10.90	5.523%	$11.502	$11.50	$11.50	$11.50
Purchase #5	$141.32	3.537%	$146.3185	$146.32	$146.30	$146.30
Purchase #6	$104.53	7.499%	$112.3687	$112.37	$112.35	$112.40
Purchase #7	$147.93	13.106%	$167.3177	$167.32	$167.30	$167.30
7 purchase totals =	$698.41		$754.3332	$754.34	$754.25	$754.40