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	$12.86	13.804%	$14.6352	$14.64	$14.65	$14.60
Purchase #2	$33.89	10.694%	$37.5142	$37.51	$37.50	$37.50
Purchase #3	$108.40	8.445%	$117.5544	$117.55	$117.55	$117.60
Purchase #4	$240.51	5.864%	$254.6135	$254.61	$254.60	$254.60
Purchase #5	$216.90	10.198%	$239.0195	$239.02	$239.00	$239.00
Purchase #6	$206.98	7.660%	$222.8347	$222.83	$222.85	$222.80
Purchase #7	$125.57	11.389%	$139.8712	$139.87	$139.85	$139.90
7 purchase totals =	$945.11		$1,026.0427	$1,026.03	$1,026.00	$1,026.00