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	$160.62	7.160%	$172.1204	$172.12	$172.10	$172.10
Purchase #2	$148.90	8.819%	$162.0315	$162.03	$162.05	$162.00
Purchase #3	$246.77	4.119%	$256.9345	$256.93	$256.95	$256.90
Purchase #4	$80.72	11.677%	$90.1457	$90.15	$90.15	$90.10
Purchase #5	$23.66	5.310%	$24.9163	$24.92	$24.90	$24.90
Purchase #6	$176.77	10.809%	$195.8771	$195.88	$195.90	$195.90
Purchase #7	$234.49	3.792%	$243.3819	$243.38	$243.40	$243.40
7 purchase totals =	$1,071.93		$1,145.4074	$1,145.41	$1,145.45	$1,145.30