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	$37.64	9.366%	$41.1654	$41.17	$41.15	$41.20
Purchase #2	$73.66	6.830%	$78.691	$78.69	$78.70	$78.70
Purchase #3	$14.99	3.321%	$15.4878	$15.49	$15.50	$15.50
Purchase #4	$166.72	8.294%	$180.5478	$180.55	$180.55	$180.50
Purchase #5	$102.69	9.740%	$112.692	$112.69	$112.70	$112.70
Purchase #6	$183.39	7.136%	$196.4767	$196.48	$196.50	$196.50
Purchase #7	$36.42	11.210%	$40.5027	$40.50	$40.50	$40.50
7 purchase totals =	$615.51		$665.5634	$665.57	$665.60	$665.60