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	$78.67	10.484%	$86.9178	$86.92	$86.90	$86.90
Purchase #2	$33.27	10.499%	$36.763	$36.76	$36.75	$36.80
Purchase #3	$215.92	12.770%	$243.493	$243.49	$243.50	$243.50
Purchase #4	$172.74	4.595%	$180.6774	$180.68	$180.70	$180.70
Purchase #5	$73.83	6.284%	$78.4695	$78.47	$78.45	$78.50
Purchase #6	$37.90	11.548%	$42.2767	$42.28	$42.30	$42.30
Purchase #7	$28.78	8.336%	$31.1791	$31.18	$31.20	$31.20
7 purchase totals =	$641.11		$699.7765	$699.78	$699.80	$699.90