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	$235.96	13.516%	$267.8524	$267.85	$267.85	$267.90
Purchase #2	$245.73	8.239%	$265.9757	$265.98	$266.00	$266.00
Purchase #3	$191.62	13.856%	$218.1709	$218.17	$218.15	$218.20
Purchase #4	$44.54	6.168%	$47.2872	$47.29	$47.30	$47.30
Purchase #5	$232.66	12.749%	$262.3218	$262.32	$262.30	$262.30
Purchase #6	$98.94	12.547%	$111.354	$111.35	$111.35	$111.40
Purchase #7	$17.75	4.304%	$18.514	$18.51	$18.50	$18.50
7 purchase totals =	$1,067.20		$1,191.4760	$1,191.47	$1,191.45	$1,191.60