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	$150.57	3.487%	$155.8204	$155.82	$155.80	$155.80
Purchase #2	$185.74	8.137%	$200.8537	$200.85	$200.85	$200.90
Purchase #3	$61.25	7.852%	$66.0594	$66.06	$66.05	$66.10
Purchase #4	$25.27	7.294%	$27.1132	$27.11	$27.10	$27.10
Purchase #5	$230.42	3.661%	$238.8557	$238.86	$238.85	$238.90
Purchase #6	$140.85	11.803%	$157.4745	$157.47	$157.45	$157.50
Purchase #7	$87.33	8.527%	$94.7766	$94.78	$94.80	$94.80
7 purchase totals =	$881.43		$940.9535	$940.95	$940.90	$941.10