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	$165.65	3.561%	$171.5488	$171.55	$171.55	$171.50
Purchase #2	$125.64	5.134%	$132.0904	$132.09	$132.10	$132.10
Purchase #3	$31.27	11.153%	$34.7575	$34.76	$34.75	$34.80
Purchase #4	$211.27	11.639%	$235.8597	$235.86	$235.85	$235.90
Purchase #5	$192.39	8.348%	$208.4507	$208.45	$208.45	$208.50
Purchase #6	$17.54	7.477%	$18.8515	$18.85	$18.85	$18.90
Purchase #7	$227.50	4.724%	$238.2471	$238.25	$238.25	$238.20
7 purchase totals =	$971.26		$1,039.8057	$1,039.81	$1,039.80	$1,039.90