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	$180.36	13.774%	$205.2028	$205.20	$205.20	$205.20
Purchase #2	$183.86	3.553%	$190.3925	$190.39	$190.40	$190.40
Purchase #3	$149.62	6.598%	$159.4919	$159.49	$159.50	$159.50
Purchase #4	$69.93	5.691%	$73.9097	$73.91	$73.90	$73.90
Purchase #5	$131.52	8.213%	$142.3217	$142.32	$142.30	$142.30
Purchase #6	$92.44	12.311%	$103.8203	$103.82	$103.80	$103.80
Purchase #7	$154.63	8.243%	$167.3762	$167.38	$167.40	$167.40
7 purchase totals =	$962.36		$1,042.5151	$1,042.51	$1,042.50	$1,042.50