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	$216.26	13.755%	$246.0066	$246.01	$246.00	$246.00
Purchase #2	$152.53	10.544%	$168.6128	$168.61	$168.60	$168.60
Purchase #3	$168.89	7.873%	$182.1867	$182.19	$182.20	$182.20
Purchase #4	$192.69	12.563%	$216.8976	$216.90	$216.90	$216.90
Purchase #5	$128.33	11.344%	$142.8878	$142.89	$142.90	$142.90
Purchase #6	$54.96	3.471%	$56.8677	$56.87	$56.85	$56.90
Purchase #7	$191.32	11.792%	$213.8805	$213.88	$213.90	$213.90
7 purchase totals =	$1,104.98		$1,227.3397	$1,227.35	$1,227.35	$1,227.40