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	$62.29	3.635%	$64.5542	$64.55	$64.55	$64.60
Purchase #2	$119.85	9.584%	$131.3364	$131.34	$131.35	$131.30
Purchase #3	$69.56	12.516%	$78.2661	$78.27	$78.25	$78.30
Purchase #4	$200.63	4.168%	$208.9923	$208.99	$209.00	$209.00
Purchase #5	$184.50	4.796%	$193.3486	$193.35	$193.35	$193.30
Purchase #6	$38.85	4.588%	$40.6324	$40.63	$40.65	$40.60
Purchase #7	$15.26	4.321%	$15.9194	$15.92	$15.90	$15.90
7 purchase totals =	$690.94		$733.0494	$733.05	$733.05	$733.00