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	$202.68	10.367%	$223.6918	$223.69	$223.70	$223.70
Purchase #2	$68.27	6.754%	$72.881	$72.88	$72.90	$72.90
Purchase #3	$213.27	4.726%	$223.3491	$223.35	$223.35	$223.30
Purchase #4	$83.29	4.651%	$87.1638	$87.16	$87.15	$87.20
Purchase #5	$28.37	11.615%	$31.6652	$31.67	$31.65	$31.70
Purchase #6	$121.45	12.687%	$136.8584	$136.86	$136.85	$136.90
Purchase #7	$38.86	11.450%	$43.3095	$43.31	$43.30	$43.30
7 purchase totals =	$756.19		$818.9188	$818.92	$818.90	$819.00