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	$213.37	12.788%	$240.6558	$240.66	$240.65	$240.70
Purchase #2	$105.69	6.380%	$112.433	$112.43	$112.45	$112.40
Purchase #3	$33.66	10.469%	$37.1839	$37.18	$37.20	$37.20
Purchase #4	$76.55	7.246%	$82.0968	$82.10	$82.10	$82.10
Purchase #5	$236.56	12.228%	$265.4866	$265.49	$265.50	$265.50
Purchase #6	$244.75	4.144%	$254.8924	$254.89	$254.90	$254.90
Purchase #7	$238.67	11.392%	$265.8593	$265.86	$265.85	$265.90
7 purchase totals =	$1,149.25		$1,258.6078	$1,258.61	$1,258.65	$1,258.70