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	$197.41	12.615%	$222.3133	$222.31	$222.30	$222.30
Purchase #2	$71.53	9.308%	$78.188	$78.19	$78.20	$78.20
Purchase #3	$178.88	6.732%	$190.9222	$190.92	$190.90	$190.90
Purchase #4	$67.46	8.134%	$72.9472	$72.95	$72.95	$72.90
Purchase #5	$125.83	10.480%	$139.017	$139.02	$139.00	$139.00
Purchase #6	$229.31	3.173%	$236.586	$236.59	$236.60	$236.60
Purchase #7	$32.79	8.299%	$35.5112	$35.51	$35.50	$35.50
7 purchase totals =	$903.21		$975.4849	$975.49	$975.45	$975.40