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	$238.34	7.566%	$256.3728	$256.37	$256.35	$256.40
Purchase #2	$142.69	5.833%	$151.0131	$151.01	$151.00	$151.00
Purchase #3	$224.58	3.222%	$231.816	$231.82	$231.80	$231.80
Purchase #4	$233.28	7.470%	$250.706	$250.71	$250.70	$250.70
Purchase #5	$117.76	4.776%	$123.3842	$123.38	$123.40	$123.40
Purchase #6	$25.47	11.525%	$28.4054	$28.41	$28.40	$28.40
Purchase #7	$55.43	12.551%	$62.387	$62.39	$62.40	$62.40
7 purchase totals =	$1,037.55		$1,104.0845	$1,104.09	$1,104.05	$1,104.10