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	$232.26	11.390%	$258.7144	$258.71	$258.70	$258.70
Purchase #2	$51.76	11.314%	$57.6161	$57.62	$57.60	$57.60
Purchase #3	$31.35	13.847%	$35.691	$35.69	$35.70	$35.70
Purchase #4	$186.47	7.131%	$199.7672	$199.77	$199.75	$199.80
Purchase #5	$37.97	10.256%	$41.8642	$41.86	$41.85	$41.90
Purchase #6	$79.32	13.659%	$90.1543	$90.15	$90.15	$90.20
Purchase #7	$184.73	8.393%	$200.2344	$200.23	$200.25	$200.20
7 purchase totals =	$803.86		$884.0416	$884.03	$884.00	$884.10