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	$38.26	6.108%	$40.5969	$40.60	$40.60	$40.60
Purchase #2	$171.87	10.785%	$190.4062	$190.41	$190.40	$190.40
Purchase #3	$61.40	5.479%	$64.7641	$64.76	$64.75	$64.80
Purchase #4	$157.51	5.216%	$165.7257	$165.73	$165.75	$165.70
Purchase #5	$199.40	10.555%	$220.4467	$220.45	$220.45	$220.40
Purchase #6	$159.88	11.138%	$177.6874	$177.69	$177.70	$177.70
Purchase #7	$70.34	3.603%	$72.8744	$72.87	$72.85	$72.90
7 purchase totals =	$858.66		$932.5014	$932.51	$932.50	$932.50