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	$192.59	12.577%	$216.812	$216.81	$216.80	$216.80
Purchase #2	$88.90	12.503%	$100.0152	$100.02	$100.00	$100.00
Purchase #3	$24.88	3.807%	$25.8272	$25.83	$25.85	$25.80
Purchase #4	$236.36	10.372%	$260.8753	$260.88	$260.90	$260.90
Purchase #5	$139.79	9.170%	$152.6087	$152.61	$152.60	$152.60
Purchase #6	$105.32	6.700%	$112.3764	$112.38	$112.40	$112.40
Purchase #7	$100.77	11.196%	$112.0522	$112.05	$112.05	$112.10
7 purchase totals =	$888.61		$980.5670	$980.58	$980.60	$980.60