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	$135.40	5.409%	$142.7238	$142.72	$142.70	$142.70
Purchase #2	$28.73	10.215%	$31.6648	$31.66	$31.65	$31.70
Purchase #3	$65.28	12.643%	$73.5334	$73.53	$73.55	$73.50
Purchase #4	$96.94	4.134%	$100.9475	$100.95	$100.95	$100.90
Purchase #5	$140.48	11.569%	$156.7321	$156.73	$156.75	$156.70
Purchase #6	$91.48	6.590%	$97.5085	$97.51	$97.50	$97.50
Purchase #7	$143.26	10.797%	$158.7278	$158.73	$158.75	$158.70
7 purchase totals =	$701.57		$761.8379	$761.83	$761.85	$761.70