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	$241.59	10.625%	$267.2589	$267.26	$267.25	$267.30
Purchase #2	$32.67	9.827%	$35.8805	$35.88	$35.90	$35.90
Purchase #3	$188.50	10.486%	$208.2661	$208.27	$208.25	$208.30
Purchase #4	$32.86	7.310%	$35.2621	$35.26	$35.25	$35.30
Purchase #5	$138.47	6.520%	$147.4982	$147.50	$147.50	$147.50
Purchase #6	$228.85	10.591%	$253.0875	$253.09	$253.10	$253.10
Purchase #7	$103.91	9.688%	$113.9768	$113.98	$114.00	$114.00
7 purchase totals =	$966.85		$1,061.2301	$1,061.24	$1,061.25	$1,061.40