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	$87.32	9.249%	$95.3962	$95.40	$95.40	$95.40
Purchase #2	$130.82	6.505%	$139.3298	$139.33	$139.35	$139.30
Purchase #3	$86.73	12.254%	$97.3579	$97.36	$97.35	$97.40
Purchase #4	$155.60	4.599%	$162.756	$162.76	$162.75	$162.80
Purchase #5	$34.71	5.422%	$36.592	$36.59	$36.60	$36.60
Purchase #6	$38.78	10.630%	$42.9023	$42.90	$42.90	$42.90
Purchase #7	$92.69	11.237%	$103.1056	$103.11	$103.10	$103.10
7 purchase totals =	$626.65		$677.4398	$677.45	$677.45	$677.50