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	$43.86	3.568%	$45.4249	$45.42	$45.40	$45.40
Purchase #2	$82.30	6.837%	$87.9269	$87.93	$87.95	$87.90
Purchase #3	$10.52	10.384%	$11.6124	$11.61	$11.60	$11.60
Purchase #4	$44.95	12.489%	$50.5638	$50.56	$50.55	$50.60
Purchase #5	$206.79	6.372%	$219.9667	$219.97	$219.95	$220.00
Purchase #6	$78.57	11.508%	$87.6118	$87.61	$87.60	$87.60
Purchase #7	$12.39	8.166%	$13.4018	$13.40	$13.40	$13.40
7 purchase totals =	$479.38		$516.5083	$516.50	$516.45	$516.50