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	$82.39	5.443%	$86.8745	$86.87	$86.85	$86.90
Purchase #2	$181.35	8.610%	$196.9642	$196.96	$196.95	$197.00
Purchase #3	$100.40	4.605%	$105.0234	$105.02	$105.00	$105.00
Purchase #4	$118.49	10.863%	$131.3616	$131.36	$131.35	$131.40
Purchase #5	$110.69	9.611%	$121.3284	$121.33	$121.35	$121.30
Purchase #6	$62.39	4.475%	$65.182	$65.18	$65.20	$65.20
Purchase #7	$139.32	13.840%	$158.6019	$158.60	$158.60	$158.60
7 purchase totals =	$795.03		$865.3360	$865.32	$865.30	$865.40