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	$33.66	10.739%	$37.2747	$37.27	$37.25	$37.30
Purchase #2	$137.95	9.828%	$151.5077	$151.51	$151.50	$151.50
Purchase #3	$18.67	8.195%	$20.2	$20.20	$20.20	$20.20
Purchase #4	$72.77	13.868%	$82.8617	$82.86	$82.85	$82.90
Purchase #5	$153.87	13.746%	$175.021	$175.02	$175.00	$175.00
Purchase #6	$72.55	8.390%	$78.6369	$78.64	$78.65	$78.60
Purchase #7	$130.36	5.498%	$137.5272	$137.53	$137.55	$137.50
7 purchase totals =	$619.83		$683.0292	$683.03	$683.00	$683.00