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	$167.62	13.583%	$190.3878	$190.39	$190.40	$190.40
Purchase #2	$130.65	4.364%	$136.3516	$136.35	$136.35	$136.40
Purchase #3	$139.37	10.741%	$154.3397	$154.34	$154.35	$154.30
Purchase #4	$161.39	5.604%	$170.4343	$170.43	$170.45	$170.40
Purchase #5	$17.97	13.459%	$20.3886	$20.39	$20.40	$20.40
Purchase #6	$180.82	5.542%	$190.841	$190.84	$190.85	$190.80
Purchase #7	$232.81	6.790%	$248.6178	$248.62	$248.60	$248.60
7 purchase totals =	$1,030.63		$1,111.3608	$1,111.36	$1,111.40	$1,111.30