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	$191.97	13.473%	$217.8341	$217.83	$217.85	$217.80
Purchase #2	$63.64	10.222%	$70.1453	$70.15	$70.15	$70.10
Purchase #3	$115.78	7.699%	$124.6939	$124.69	$124.70	$124.70
Purchase #4	$234.50	9.274%	$256.2475	$256.25	$256.25	$256.20
Purchase #5	$207.54	8.556%	$225.2971	$225.30	$225.30	$225.30
Purchase #6	$90.25	5.411%	$95.1334	$95.13	$95.15	$95.10
Purchase #7	$52.28	13.822%	$59.5061	$59.51	$59.50	$59.50
7 purchase totals =	$955.96		$1,048.8574	$1,048.86	$1,048.90	$1,048.70