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	$171.90	10.863%	$190.5735	$190.57	$190.55	$190.60
Purchase #2	$243.87	13.289%	$276.2779	$276.28	$276.30	$276.30
Purchase #3	$64.98	11.434%	$72.4098	$72.41	$72.40	$72.40
Purchase #4	$155.54	3.541%	$161.0477	$161.05	$161.05	$161.00
Purchase #5	$242.76	5.431%	$255.9443	$255.94	$255.95	$255.90
Purchase #6	$12.94	6.359%	$13.7629	$13.76	$13.75	$13.80
Purchase #7	$90.89	8.344%	$98.4739	$98.47	$98.45	$98.50
7 purchase totals =	$982.88		$1,068.4900	$1,068.48	$1,068.45	$1,068.50