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	$152.26	4.143%	$158.5681	$158.57	$158.55	$158.60
Purchase #2	$77.65	10.351%	$85.6876	$85.69	$85.70	$85.70
Purchase #3	$64.65	11.516%	$72.0951	$72.10	$72.10	$72.10
Purchase #4	$132.78	5.558%	$140.1599	$140.16	$140.15	$140.20
Purchase #5	$140.38	11.134%	$156.0099	$156.01	$156.00	$156.00
Purchase #6	$224.88	8.318%	$243.5855	$243.59	$243.60	$243.60
Purchase #7	$24.39	13.868%	$27.7724	$27.77	$27.75	$27.80
7 purchase totals =	$816.99		$883.8785	$883.89	$883.85	$884.00