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	$39.85	13.111%	$45.0747	$45.07	$45.05	$45.10
Purchase #2	$62.78	9.847%	$68.9619	$68.96	$68.95	$69.00
Purchase #3	$53.96	10.846%	$59.8125	$59.81	$59.80	$59.80
Purchase #4	$78.89	7.778%	$85.0261	$85.03	$85.05	$85.00
Purchase #5	$158.31	4.623%	$165.6287	$165.63	$165.65	$165.60
Purchase #6	$229.25	12.372%	$257.6128	$257.61	$257.60	$257.60
Purchase #7	$12.57	13.310%	$14.2431	$14.24	$14.25	$14.20
7 purchase totals =	$635.61		$696.3598	$696.35	$696.35	$696.30