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	$108.66	13.540%	$123.3726	$123.37	$123.35	$123.40
Purchase #2	$86.59	11.313%	$96.3859	$96.39	$96.40	$96.40
Purchase #3	$84.48	12.566%	$95.0958	$95.10	$95.10	$95.10
Purchase #4	$38.99	7.531%	$41.9263	$41.93	$41.95	$41.90
Purchase #5	$66.82	9.145%	$72.9307	$72.93	$72.95	$72.90
Purchase #6	$142.77	5.401%	$150.481	$150.48	$150.50	$150.50
Purchase #7	$5.53	12.303%	$6.2104	$6.21	$6.20	$6.20
7 purchase totals =	$533.84		$586.4027	$586.41	$586.45	$586.40