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	$80.78	8.248%	$87.4427	$87.44	$87.45	$87.40
Purchase #2	$13.32	8.453%	$14.4459	$14.45	$14.45	$14.40
Purchase #3	$207.76	5.174%	$218.5095	$218.51	$218.50	$218.50
Purchase #4	$112.34	4.371%	$117.2504	$117.25	$117.25	$117.30
Purchase #5	$100.77	8.337%	$109.1712	$109.17	$109.15	$109.20
Purchase #6	$176.41	7.789%	$190.1506	$190.15	$190.15	$190.20
Purchase #7	$69.89	3.234%	$72.1502	$72.15	$72.15	$72.20
7 purchase totals =	$761.27		$809.1205	$809.12	$809.10	$809.20