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	$250.55	4.127%	$260.8902	$260.89	$260.90	$260.90
Purchase #2	$196.25	7.445%	$210.8608	$210.86	$210.85	$210.90
Purchase #3	$40.62	3.153%	$41.9007	$41.90	$41.90	$41.90
Purchase #4	$210.59	10.551%	$232.8094	$232.81	$232.80	$232.80
Purchase #5	$17.82	8.308%	$19.3005	$19.30	$19.30	$19.30
Purchase #6	$34.76	9.163%	$37.9451	$37.95	$37.95	$37.90
Purchase #7	$67.26	6.716%	$71.7772	$71.78	$71.80	$71.80
7 purchase totals =	$817.85		$875.4839	$875.49	$875.50	$875.50