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	$150.57	3.665%	$156.0884	$156.09	$156.10	$156.10
Purchase #2	$5.65	10.853%	$6.2632	$6.26	$6.25	$6.30
Purchase #3	$242.68	8.320%	$262.871	$262.87	$262.85	$262.90
Purchase #4	$111.71	11.345%	$124.3835	$124.38	$124.40	$124.40
Purchase #5	$22.89	6.114%	$24.2895	$24.29	$24.30	$24.30
Purchase #6	$171.33	8.239%	$185.4459	$185.45	$185.45	$185.40
Purchase #7	$117.96	12.661%	$132.8949	$132.89	$132.90	$132.90
7 purchase totals =	$822.79		$892.2364	$892.23	$892.25	$892.30