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	$247.89	13.658%	$281.7468	$281.75	$281.75	$281.70
Purchase #2	$29.98	6.176%	$31.8316	$31.83	$31.85	$31.80
Purchase #3	$136.69	9.851%	$150.1553	$150.16	$150.15	$150.20
Purchase #4	$117.94	3.333%	$121.8709	$121.87	$121.85	$121.90
Purchase #5	$127.37	3.216%	$131.4662	$131.47	$131.45	$131.50
Purchase #6	$244.77	10.178%	$269.6827	$269.68	$269.70	$269.70
Purchase #7	$161.89	12.868%	$182.722	$182.72	$182.70	$182.70
7 purchase totals =	$1,066.53		$1,169.4755	$1,169.48	$1,169.45	$1,169.50