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	$117.28	13.704%	$133.3521	$133.35	$133.35	$133.40
Purchase #2	$59.30	5.364%	$62.4809	$62.48	$62.50	$62.50
Purchase #3	$167.35	11.287%	$186.2388	$186.24	$186.25	$186.20
Purchase #4	$218.38	3.456%	$225.9272	$225.93	$225.95	$225.90
Purchase #5	$78.35	6.841%	$83.7099	$83.71	$83.70	$83.70
Purchase #6	$59.29	5.636%	$62.6316	$62.63	$62.65	$62.60
Purchase #7	$111.86	10.384%	$123.4755	$123.48	$123.50	$123.50
7 purchase totals =	$811.81		$877.8160	$877.82	$877.90	$877.80