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	$135.71	11.445%	$151.242	$151.24	$151.25	$151.20
Purchase #2	$75.48	4.512%	$78.8857	$78.89	$78.90	$78.90
Purchase #3	$79.39	13.608%	$90.1934	$90.19	$90.20	$90.20
Purchase #4	$58.37	5.417%	$61.5319	$61.53	$61.55	$61.50
Purchase #5	$148.68	6.676%	$158.6059	$158.61	$158.60	$158.60
Purchase #6	$169.31	5.474%	$178.578	$178.58	$178.60	$178.60
Purchase #7	$19.71	10.191%	$21.7186	$21.72	$21.70	$21.70
7 purchase totals =	$686.65		$740.7555	$740.76	$740.80	$740.70