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	$41.31	5.168%	$43.4449	$43.44	$43.45	$43.40
Purchase #2	$40.60	3.756%	$42.1249	$42.12	$42.10	$42.10
Purchase #3	$237.56	10.687%	$262.948	$262.95	$262.95	$262.90
Purchase #4	$146.53	12.253%	$164.4843	$164.48	$164.50	$164.50
Purchase #5	$75.77	8.714%	$82.3726	$82.37	$82.35	$82.40
Purchase #6	$47.76	9.597%	$52.3435	$52.34	$52.35	$52.30
Purchase #7	$247.31	13.507%	$280.7142	$280.71	$280.70	$280.70
7 purchase totals =	$836.84		$928.4324	$928.41	$928.40	$928.30