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	$141.56	8.666%	$153.8276	$153.83	$153.85	$153.80
Purchase #2	$82.32	11.338%	$91.6534	$91.65	$91.65	$91.70
Purchase #3	$177.57	11.619%	$198.2019	$198.20	$198.20	$198.20
Purchase #4	$31.25	3.786%	$32.4331	$32.43	$32.45	$32.40
Purchase #5	$52.29	4.799%	$54.7994	$54.80	$54.80	$54.80
Purchase #6	$228.89	4.165%	$238.4233	$238.42	$238.40	$238.40
Purchase #7	$148.81	3.269%	$153.6746	$153.67	$153.65	$153.70
7 purchase totals =	$862.69		$923.0133	$923.00	$923.00	$923.00