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	$175.49	8.532%	$190.4628	$190.46	$190.45	$190.50
Purchase #2	$92.25	7.771%	$99.4187	$99.42	$99.40	$99.40
Purchase #3	$57.81	12.602%	$65.0952	$65.10	$65.10	$65.10
Purchase #4	$184.28	8.827%	$200.5464	$200.55	$200.55	$200.50
Purchase #5	$69.31	11.304%	$77.1448	$77.14	$77.15	$77.10
Purchase #6	$37.36	13.128%	$42.2646	$42.26	$42.25	$42.30
Purchase #7	$88.89	7.484%	$95.5425	$95.54	$95.55	$95.50
7 purchase totals =	$705.39		$770.4750	$770.47	$770.45	$770.40