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	$85.30	3.735%	$88.486	$88.49	$88.50	$88.50
Purchase #2	$20.58	5.581%	$21.7286	$21.73	$21.75	$21.70
Purchase #3	$143.98	5.660%	$152.1293	$152.13	$152.15	$152.10
Purchase #4	$211.70	5.139%	$222.5793	$222.58	$222.60	$222.60
Purchase #5	$95.87	9.109%	$104.6028	$104.60	$104.60	$104.60
Purchase #6	$23.83	6.782%	$25.4462	$25.45	$25.45	$25.40
Purchase #7	$7.61	3.132%	$7.8483	$7.85	$7.85	$7.80
7 purchase totals =	$588.87		$622.8205	$622.83	$622.90	$622.70