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	$65.65	12.561%	$73.8963	$73.90	$73.90	$73.90
Purchase #2	$112.59	4.339%	$117.4753	$117.48	$117.50	$117.50
Purchase #3	$10.76	4.574%	$11.2522	$11.25	$11.25	$11.30
Purchase #4	$41.79	4.137%	$43.5189	$43.52	$43.50	$43.50
Purchase #5	$244.64	11.714%	$273.2971	$273.30	$273.30	$273.30
Purchase #6	$221.91	4.289%	$231.4277	$231.43	$231.45	$231.40
Purchase #7	$9.85	6.322%	$10.4727	$10.47	$10.45	$10.50
7 purchase totals =	$707.19		$761.3402	$761.35	$761.35	$761.40