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	$211.79	9.393%	$231.6834	$231.68	$231.70	$231.70
Purchase #2	$137.38	4.572%	$143.661	$143.66	$143.65	$143.70
Purchase #3	$164.44	10.450%	$181.624	$181.62	$181.60	$181.60
Purchase #4	$99.45	11.630%	$111.016	$111.02	$111.00	$111.00
Purchase #5	$169.92	13.411%	$192.708	$192.71	$192.70	$192.70
Purchase #6	$33.71	10.270%	$37.172	$37.17	$37.15	$37.20
Purchase #7	$59.84	13.463%	$67.8963	$67.90	$67.90	$67.90
7 purchase totals =	$876.53		$965.7607	$965.76	$965.70	$965.80