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	$186.34	4.428%	$194.5911	$194.59	$194.60	$194.60
Purchase #2	$60.42	9.246%	$66.0064	$66.01	$66.00	$66.00
Purchase #3	$10.98	13.220%	$12.4316	$12.43	$12.45	$12.40
Purchase #4	$185.39	8.270%	$200.7218	$200.72	$200.70	$200.70
Purchase #5	$138.64	9.148%	$151.3228	$151.32	$151.30	$151.30
Purchase #6	$35.90	10.134%	$39.5381	$39.54	$39.55	$39.50
Purchase #7	$40.27	10.601%	$44.539	$44.54	$44.55	$44.50
7 purchase totals =	$657.94		$709.1508	$709.15	$709.15	$709.00