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	$188.98	12.202%	$212.0393	$212.04	$212.05	$212.00
Purchase #2	$99.63	9.870%	$109.4635	$109.46	$109.45	$109.50
Purchase #3	$231.54	9.185%	$252.8069	$252.81	$252.80	$252.80
Purchase #4	$92.85	13.714%	$105.5834	$105.58	$105.60	$105.60
Purchase #5	$12.30	10.361%	$13.5744	$13.57	$13.55	$13.60
Purchase #6	$200.83	5.314%	$211.5021	$211.50	$211.50	$211.50
Purchase #7	$67.67	13.563%	$76.8481	$76.85	$76.85	$76.80
7 purchase totals =	$893.80		$981.8177	$981.81	$981.80	$981.80