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	$153.93	11.225%	$171.2086	$171.21	$171.20	$171.20
Purchase #2	$117.50	12.577%	$132.278	$132.28	$132.30	$132.30
Purchase #3	$94.66	9.274%	$103.4388	$103.44	$103.45	$103.40
Purchase #4	$158.37	9.181%	$172.9099	$172.91	$172.90	$172.90
Purchase #5	$133.95	5.852%	$141.7888	$141.79	$141.80	$141.80
Purchase #6	$120.27	9.284%	$131.4359	$131.44	$131.45	$131.40
Purchase #7	$181.97	3.254%	$187.8913	$187.89	$187.90	$187.90
7 purchase totals =	$960.65		$1,040.9513	$1,040.96	$1,041.00	$1,040.90