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	$236.83	8.503%	$256.9677	$256.97	$256.95	$257.00
Purchase #2	$77.29	3.506%	$79.9998	$80.00	$80.00	$80.00
Purchase #3	$143.95	10.311%	$158.7927	$158.79	$158.80	$158.80
Purchase #4	$192.42	8.607%	$208.9816	$208.98	$209.00	$209.00
Purchase #5	$40.73	3.404%	$42.1164	$42.12	$42.10	$42.10
Purchase #6	$31.58	6.444%	$33.615	$33.62	$33.60	$33.60
Purchase #7	$101.77	3.503%	$105.335	$105.34	$105.35	$105.30
7 purchase totals =	$824.57		$885.8082	$885.82	$885.80	$885.80