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	$49.26	13.520%	$55.92	$55.92	$55.90	$55.90
Purchase #2	$78.50	11.185%	$87.2802	$87.28	$87.30	$87.30
Purchase #3	$100.49	4.291%	$104.802	$104.80	$104.80	$104.80
Purchase #4	$198.63	12.121%	$222.7059	$222.71	$222.70	$222.70
Purchase #5	$131.53	13.178%	$148.863	$148.86	$148.85	$148.90
Purchase #6	$5.77	9.148%	$6.2978	$6.30	$6.30	$6.30
Purchase #7	$95.56	8.442%	$103.6272	$103.63	$103.65	$103.60
7 purchase totals =	$659.74		$729.4961	$729.50	$729.50	$729.50