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	$175.71	5.778%	$185.8625	$185.86	$185.85	$185.90
Purchase #2	$5.57	6.731%	$5.9449	$5.94	$5.95	$5.90
Purchase #3	$85.50	6.249%	$90.8429	$90.84	$90.85	$90.80
Purchase #4	$110.48	12.117%	$123.8669	$123.87	$123.85	$123.90
Purchase #5	$38.92	7.298%	$41.7604	$41.76	$41.75	$41.80
Purchase #6	$21.71	13.321%	$24.602	$24.60	$24.60	$24.60
Purchase #7	$99.88	13.282%	$113.1461	$113.15	$113.15	$113.10
7 purchase totals =	$537.77		$586.0257	$586.02	$586.00	$586.00