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	$216.40	8.208%	$234.1621	$234.16	$234.15	$234.20
Purchase #2	$222.68	4.328%	$232.3176	$232.32	$232.30	$232.30
Purchase #3	$143.39	11.302%	$159.5959	$159.60	$159.60	$159.60
Purchase #4	$151.81	11.225%	$168.8507	$168.85	$168.85	$168.90
Purchase #5	$82.71	9.445%	$90.522	$90.52	$90.50	$90.50
Purchase #6	$213.38	4.283%	$222.5191	$222.52	$222.50	$222.50
Purchase #7	$99.31	8.530%	$107.7811	$107.78	$107.80	$107.80
7 purchase totals =	$1,129.68		$1,215.7485	$1,215.75	$1,215.70	$1,215.80