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	$138.71	10.165%	$152.8099	$152.81	$152.80	$152.80
Purchase #2	$237.66	10.282%	$262.0962	$262.10	$262.10	$262.10
Purchase #3	$140.98	3.514%	$145.934	$145.93	$145.95	$145.90
Purchase #4	$240.33	13.831%	$273.57	$273.57	$273.55	$273.60
Purchase #5	$173.85	9.594%	$190.5292	$190.53	$190.55	$190.50
Purchase #6	$150.90	13.219%	$170.8475	$170.85	$170.85	$170.80
Purchase #7	$17.58	5.754%	$18.5916	$18.59	$18.60	$18.60
7 purchase totals =	$1,100.01		$1,214.3784	$1,214.38	$1,214.40	$1,214.30