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	$87.79	4.630%	$91.8547	$91.85	$91.85	$91.90
Purchase #2	$213.42	11.447%	$237.8502	$237.85	$237.85	$237.90
Purchase #3	$228.86	11.247%	$254.5999	$254.60	$254.60	$254.60
Purchase #4	$180.46	4.666%	$188.8803	$188.88	$188.90	$188.90
Purchase #5	$48.27	7.737%	$52.0046	$52.00	$52.00	$52.00
Purchase #6	$127.63	7.221%	$136.8462	$136.85	$136.85	$136.80
Purchase #7	$18.47	10.827%	$20.4697	$20.47	$20.45	$20.50
7 purchase totals =	$904.90		$982.5056	$982.50	$982.50	$982.60