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	$50.84	13.371%	$57.6378	$57.64	$57.65	$57.60
Purchase #2	$205.25	8.315%	$222.3165	$222.32	$222.30	$222.30
Purchase #3	$245.79	4.507%	$256.8678	$256.87	$256.85	$256.90
Purchase #4	$243.91	4.497%	$254.8786	$254.88	$254.90	$254.90
Purchase #5	$179.64	7.725%	$193.5172	$193.52	$193.50	$193.50
Purchase #6	$74.28	5.792%	$78.5823	$78.58	$78.60	$78.60
Purchase #7	$111.29	5.284%	$117.1706	$117.17	$117.15	$117.20
7 purchase totals =	$1,111.00		$1,180.9708	$1,180.98	$1,180.95	$1,181.00