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	$54.36	6.602%	$57.9488	$57.95	$57.95	$57.90
Purchase #2	$38.94	7.445%	$41.8391	$41.84	$41.85	$41.80
Purchase #3	$196.50	3.510%	$203.3972	$203.40	$203.40	$203.40
Purchase #4	$80.48	3.281%	$83.1205	$83.12	$83.10	$83.10
Purchase #5	$79.36	5.579%	$83.7875	$83.79	$83.80	$83.80
Purchase #6	$43.88	3.703%	$45.5049	$45.50	$45.50	$45.50
Purchase #7	$192.25	3.796%	$199.5478	$199.55	$199.55	$199.50
7 purchase totals =	$685.77		$715.1458	$715.15	$715.15	$715.00