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	$57.33	13.473%	$65.0541	$65.05	$65.05	$65.10
Purchase #2	$199.55	8.197%	$215.9071	$215.91	$215.90	$215.90
Purchase #3	$241.56	13.386%	$273.8952	$273.90	$273.90	$273.90
Purchase #4	$199.95	8.853%	$217.6516	$217.65	$217.65	$217.70
Purchase #5	$35.31	6.178%	$37.4915	$37.49	$37.50	$37.50
Purchase #6	$47.65	4.202%	$49.6523	$49.65	$49.65	$49.70
Purchase #7	$227.48	12.746%	$256.4746	$256.47	$256.45	$256.50
7 purchase totals =	$1,008.83		$1,116.1264	$1,116.12	$1,116.10	$1,116.30