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	$150.41	12.333%	$168.9601	$168.96	$168.95	$169.00
Purchase #2	$52.28	9.507%	$57.2503	$57.25	$57.25	$57.30
Purchase #3	$82.87	3.526%	$85.792	$85.79	$85.80	$85.80
Purchase #4	$238.78	7.434%	$256.5309	$256.53	$256.55	$256.50
Purchase #5	$84.28	4.292%	$87.8973	$87.90	$87.90	$87.90
Purchase #6	$240.76	4.611%	$251.8614	$251.86	$251.85	$251.90
Purchase #7	$212.36	7.336%	$227.9387	$227.94	$227.95	$227.90
7 purchase totals =	$1,061.74		$1,136.2307	$1,136.23	$1,136.25	$1,136.30