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	$198.47	3.639%	$205.6923	$205.69	$205.70	$205.70
Purchase #2	$64.89	6.648%	$69.2039	$69.20	$69.20	$69.20
Purchase #3	$63.79	4.873%	$66.8985	$66.90	$66.90	$66.90
Purchase #4	$90.65	11.841%	$101.3839	$101.38	$101.40	$101.40
Purchase #5	$8.50	4.762%	$8.9048	$8.90	$8.90	$8.90
Purchase #6	$45.95	12.474%	$51.6818	$51.68	$51.70	$51.70
Purchase #7	$155.66	5.391%	$164.0516	$164.05	$164.05	$164.10
7 purchase totals =	$627.91		$667.8168	$667.80	$667.85	$667.90