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	$24.33	4.503%	$25.4256	$25.43	$25.45	$25.40
Purchase #2	$247.52	9.181%	$270.2448	$270.24	$270.25	$270.20
Purchase #3	$98.79	5.591%	$104.3133	$104.31	$104.30	$104.30
Purchase #4	$250.88	11.828%	$280.5541	$280.55	$280.55	$280.60
Purchase #5	$132.61	6.539%	$141.2814	$141.28	$141.30	$141.30
Purchase #6	$161.39	6.873%	$172.4823	$172.48	$172.50	$172.50
Purchase #7	$40.60	4.595%	$42.4656	$42.47	$42.45	$42.50
7 purchase totals =	$956.12		$1,036.7671	$1,036.76	$1,036.80	$1,036.80