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	$33.55	6.257%	$35.6492	$35.65	$35.65	$35.60
Purchase #2	$133.50	5.551%	$140.9106	$140.91	$140.90	$140.90
Purchase #3	$164.26	6.216%	$174.4704	$174.47	$174.45	$174.50
Purchase #4	$78.86	4.800%	$82.6453	$82.65	$82.65	$82.60
Purchase #5	$20.94	6.341%	$22.2678	$22.27	$22.25	$22.30
Purchase #6	$215.45	10.257%	$237.5487	$237.55	$237.55	$237.50
Purchase #7	$175.82	7.211%	$188.4984	$188.50	$188.50	$188.50
7 purchase totals =	$822.38		$881.9904	$882.00	$881.95	$881.90