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	$64.64	12.209%	$72.5319	$72.53	$72.55	$72.50
Purchase #2	$76.95	11.124%	$85.5099	$85.51	$85.50	$85.50
Purchase #3	$204.64	6.753%	$218.4593	$218.46	$218.45	$218.50
Purchase #4	$9.73	3.723%	$10.0922	$10.09	$10.10	$10.10
Purchase #5	$175.45	9.177%	$191.551	$191.55	$191.55	$191.60
Purchase #6	$68.78	7.338%	$73.8271	$73.83	$73.85	$73.80
Purchase #7	$57.83	11.661%	$64.5736	$64.57	$64.55	$64.60
7 purchase totals =	$658.02		$716.5450	$716.54	$716.55	$716.60