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	$79.40	3.672%	$82.3156	$82.32	$82.30	$82.30
Purchase #2	$71.89	8.356%	$77.8971	$77.90	$77.90	$77.90
Purchase #3	$173.85	8.133%	$187.9892	$187.99	$188.00	$188.00
Purchase #4	$38.89	5.172%	$40.9014	$40.90	$40.90	$40.90
Purchase #5	$119.59	12.461%	$134.4921	$134.49	$134.50	$134.50
Purchase #6	$152.58	7.811%	$164.498	$164.50	$164.50	$164.50
Purchase #7	$240.67	3.250%	$248.4918	$248.49	$248.50	$248.50
7 purchase totals =	$876.87		$936.5852	$936.59	$936.60	$936.60