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	$67.59	13.813%	$76.9262	$76.93	$76.95	$76.90
Purchase #2	$41.93	4.739%	$43.9171	$43.92	$43.90	$43.90
Purchase #3	$7.92	6.566%	$8.44	$8.44	$8.45	$8.40
Purchase #4	$111.69	10.376%	$123.279	$123.28	$123.30	$123.30
Purchase #5	$32.45	12.477%	$36.4988	$36.50	$36.50	$36.50
Purchase #6	$33.60	9.797%	$36.8918	$36.89	$36.90	$36.90
Purchase #7	$137.84	4.564%	$144.131	$144.13	$144.15	$144.10
7 purchase totals =	$433.02		$470.0839	$470.09	$470.15	$470.00