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	$32.68	3.157%	$33.7117	$33.71	$33.70	$33.70
Purchase #2	$24.65	10.825%	$27.3184	$27.32	$27.30	$27.30
Purchase #3	$173.91	8.597%	$188.861	$188.86	$188.85	$188.90
Purchase #4	$83.90	3.214%	$86.5965	$86.60	$86.60	$86.60
Purchase #5	$225.53	13.437%	$255.8345	$255.83	$255.85	$255.80
Purchase #6	$162.80	8.269%	$176.2619	$176.26	$176.25	$176.30
Purchase #7	$222.31	8.519%	$241.2486	$241.25	$241.25	$241.20
7 purchase totals =	$925.78		$1,009.8326	$1,009.83	$1,009.80	$1,009.80