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	$132.97	6.320%	$141.3737	$141.37	$141.35	$141.40
Purchase #2	$50.38	10.122%	$55.4795	$55.48	$55.50	$55.50
Purchase #3	$163.81	11.578%	$182.7759	$182.78	$182.80	$182.80
Purchase #4	$53.79	13.509%	$61.0565	$61.06	$61.05	$61.10
Purchase #5	$121.42	12.251%	$136.2952	$136.30	$136.30	$136.30
Purchase #6	$232.66	9.220%	$254.1113	$254.11	$254.10	$254.10
Purchase #7	$105.86	6.570%	$112.815	$112.82	$112.80	$112.80
7 purchase totals =	$860.89		$943.9071	$943.92	$943.90	$944.00