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	$242.67	4.674%	$254.0124	$254.01	$254.00	$254.00
Purchase #2	$81.66	4.526%	$85.3559	$85.36	$85.35	$85.40
Purchase #3	$139.67	13.188%	$158.0897	$158.09	$158.10	$158.10
Purchase #4	$224.69	3.183%	$231.8419	$231.84	$231.85	$231.80
Purchase #5	$30.28	4.424%	$31.6196	$31.62	$31.60	$31.60
Purchase #6	$126.28	10.527%	$139.5735	$139.57	$139.55	$139.60
Purchase #7	$64.66	11.485%	$72.0862	$72.09	$72.10	$72.10
7 purchase totals =	$909.91		$972.5792	$972.58	$972.55	$972.60