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	$131.96	3.322%	$136.3437	$136.34	$136.35	$136.30
Purchase #2	$45.99	10.397%	$50.7716	$50.77	$50.75	$50.80
Purchase #3	$47.50	11.417%	$52.9231	$52.92	$52.90	$52.90
Purchase #4	$167.69	5.226%	$176.4535	$176.45	$176.45	$176.50
Purchase #5	$35.78	13.365%	$40.562	$40.56	$40.55	$40.60
Purchase #6	$41.41	5.560%	$43.7124	$43.71	$43.70	$43.70
Purchase #7	$192.73	7.184%	$206.5757	$206.58	$206.60	$206.60
7 purchase totals =	$663.06		$707.3420	$707.33	$707.30	$707.40