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	$80.60	6.589%	$85.9107	$85.91	$85.90	$85.90
Purchase #2	$112.43	11.312%	$125.1481	$125.15	$125.15	$125.10
Purchase #3	$203.99	10.588%	$225.5885	$225.59	$225.60	$225.60
Purchase #4	$243.87	5.221%	$256.6025	$256.60	$256.60	$256.60
Purchase #5	$178.51	11.607%	$199.2297	$199.23	$199.25	$199.20
Purchase #6	$183.45	6.846%	$196.009	$196.01	$196.00	$196.00
Purchase #7	$203.28	9.538%	$222.6688	$222.67	$222.65	$222.70
7 purchase totals =	$1,206.13		$1,311.1573	$1,311.16	$1,311.15	$1,311.10