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	$207.46	5.203%	$218.2541	$218.25	$218.25	$218.30
Purchase #2	$176.40	13.474%	$200.1681	$200.17	$200.15	$200.20
Purchase #3	$65.38	11.184%	$72.6921	$72.69	$72.70	$72.70
Purchase #4	$122.45	10.138%	$134.864	$134.86	$134.85	$134.90
Purchase #5	$37.80	10.759%	$41.8669	$41.87	$41.85	$41.90
Purchase #6	$150.69	6.127%	$159.9228	$159.92	$159.90	$159.90
Purchase #7	$51.37	11.319%	$57.1846	$57.18	$57.20	$57.20
7 purchase totals =	$811.55		$884.9526	$884.94	$884.90	$885.10