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	$95.97	11.227%	$106.7446	$106.74	$106.75	$106.70
Purchase #2	$155.34	12.359%	$174.5385	$174.54	$174.55	$174.50
Purchase #3	$127.89	12.265%	$143.5757	$143.58	$143.60	$143.60
Purchase #4	$57.53	3.783%	$59.7064	$59.71	$59.70	$59.70
Purchase #5	$44.96	10.855%	$49.8404	$49.84	$49.85	$49.80
Purchase #6	$227.29	11.521%	$253.4761	$253.48	$253.50	$253.50
Purchase #7	$236.54	9.586%	$259.2147	$259.21	$259.20	$259.20
7 purchase totals =	$945.52		$1,047.0964	$1,047.10	$1,047.15	$1,047.00