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	$231.61	7.657%	$249.3444	$249.34	$249.35	$249.30
Purchase #2	$177.62	4.425%	$185.4797	$185.48	$185.50	$185.50
Purchase #3	$234.58	5.530%	$247.5523	$247.55	$247.55	$247.60
Purchase #4	$198.64	10.398%	$219.2946	$219.29	$219.30	$219.30
Purchase #5	$87.67	9.315%	$95.8365	$95.84	$95.85	$95.80
Purchase #6	$27.44	5.769%	$29.023	$29.02	$29.00	$29.00
Purchase #7	$57.39	3.761%	$59.5484	$59.55	$59.55	$59.50
7 purchase totals =	$1,014.95		$1,086.0789	$1,086.07	$1,086.10	$1,086.00