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	$34.69	4.802%	$36.3558	$36.36	$36.35	$36.40
Purchase #2	$197.38	4.166%	$205.6029	$205.60	$205.60	$205.60
Purchase #3	$207.59	12.672%	$233.8958	$233.90	$233.90	$233.90
Purchase #4	$41.25	4.428%	$43.0766	$43.08	$43.10	$43.10
Purchase #5	$32.99	11.822%	$36.8901	$36.89	$36.90	$36.90
Purchase #6	$69.48	3.219%	$71.7166	$71.72	$71.70	$71.70
Purchase #7	$41.52	4.783%	$43.5059	$43.51	$43.50	$43.50
7 purchase totals =	$624.90		$671.0437	$671.06	$671.05	$671.10