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	$203.75	9.852%	$223.8235	$223.82	$223.80	$223.80
Purchase #2	$202.43	4.677%	$211.8977	$211.90	$211.90	$211.90
Purchase #3	$38.84	9.696%	$42.6059	$42.61	$42.60	$42.60
Purchase #4	$94.83	3.226%	$97.8892	$97.89	$97.90	$97.90
Purchase #5	$91.73	10.105%	$100.9993	$101.00	$101.00	$101.00
Purchase #6	$9.57	7.688%	$10.3057	$10.31	$10.30	$10.30
Purchase #7	$43.71	10.626%	$48.3546	$48.35	$48.35	$48.40
7 purchase totals =	$684.86		$735.8759	$735.88	$735.85	$735.90