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	$196.47	6.704%	$209.6413	$209.64	$209.65	$209.60
Purchase #2	$39.47	12.352%	$44.3453	$44.35	$44.35	$44.30
Purchase #3	$29.36	5.603%	$31.005	$31.01	$31.00	$31.00
Purchase #4	$239.76	6.620%	$255.6321	$255.63	$255.65	$255.60
Purchase #5	$224.30	7.360%	$240.8085	$240.81	$240.80	$240.80
Purchase #6	$152.52	13.545%	$173.1788	$173.18	$173.20	$173.20
Purchase #7	$121.28	7.739%	$130.6659	$130.67	$130.65	$130.70
7 purchase totals =	$1,003.16		$1,085.2769	$1,085.29	$1,085.30	$1,085.20