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	$127.44	3.160%	$131.4671	$131.47	$131.45	$131.50
Purchase #2	$57.91	9.280%	$63.284	$63.28	$63.30	$63.30
Purchase #3	$165.94	8.146%	$179.4575	$179.46	$179.45	$179.50
Purchase #4	$27.35	3.791%	$28.3868	$28.39	$28.40	$28.40
Purchase #5	$208.33	3.665%	$215.9653	$215.97	$215.95	$216.00
Purchase #6	$34.78	10.128%	$38.3025	$38.30	$38.30	$38.30
Purchase #7	$12.78	6.352%	$13.5918	$13.59	$13.60	$13.60
7 purchase totals =	$634.53		$670.4550	$670.46	$670.45	$670.60