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	$143.43	9.541%	$157.1147	$157.11	$157.10	$157.10
Purchase #2	$93.77	12.690%	$105.6694	$105.67	$105.65	$105.70
Purchase #3	$222.78	9.314%	$243.5297	$243.53	$243.55	$243.50
Purchase #4	$91.45	13.785%	$104.0564	$104.06	$104.05	$104.10
Purchase #5	$83.60	4.179%	$87.0936	$87.09	$87.10	$87.10
Purchase #6	$153.71	9.298%	$168.002	$168.00	$168.00	$168.00
Purchase #7	$250.41	12.535%	$281.7989	$281.80	$281.80	$281.80
7 purchase totals =	$1,039.15		$1,147.2647	$1,147.26	$1,147.25	$1,147.30