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	$179.44	9.366%	$196.2464	$196.25	$196.25	$196.20
Purchase #2	$36.99	9.365%	$40.4541	$40.45	$40.45	$40.50
Purchase #3	$234.50	10.423%	$258.9419	$258.94	$258.95	$258.90
Purchase #4	$167.86	3.873%	$174.3612	$174.36	$174.35	$174.40
Purchase #5	$176.36	5.505%	$186.0686	$186.07	$186.05	$186.10
Purchase #6	$248.96	5.552%	$262.7823	$262.78	$262.80	$262.80
Purchase #7	$162.26	12.808%	$183.0423	$183.04	$183.05	$183.00
7 purchase totals =	$1,206.37		$1,301.8968	$1,301.89	$1,301.90	$1,301.90