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	$133.92	4.624%	$140.1125	$140.11	$140.10	$140.10
Purchase #2	$205.73	9.565%	$225.4081	$225.41	$225.40	$225.40
Purchase #3	$10.79	7.421%	$11.5907	$11.59	$11.60	$11.60
Purchase #4	$186.47	4.844%	$195.5026	$195.50	$195.50	$195.50
Purchase #5	$92.25	5.225%	$97.0701	$97.07	$97.05	$97.10
Purchase #6	$171.67	11.660%	$191.6867	$191.69	$191.70	$191.70
Purchase #7	$189.86	3.508%	$196.5203	$196.52	$196.50	$196.50
7 purchase totals =	$990.69		$1,057.8910	$1,057.89	$1,057.85	$1,057.90