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	$151.47	9.422%	$165.7415	$165.74	$165.75	$165.70
Purchase #2	$112.76	9.602%	$123.5872	$123.59	$123.60	$123.60
Purchase #3	$210.96	9.854%	$231.748	$231.75	$231.75	$231.70
Purchase #4	$125.83	4.175%	$131.0834	$131.08	$131.10	$131.10
Purchase #5	$223.45	11.433%	$248.997	$249.00	$249.00	$249.00
Purchase #6	$6.98	10.646%	$7.7231	$7.72	$7.70	$7.70
Purchase #7	$155.43	6.707%	$165.8547	$165.85	$165.85	$165.90
7 purchase totals =	$986.88		$1,074.7349	$1,074.73	$1,074.75	$1,074.70