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	$177.96	4.256%	$185.534	$185.53	$185.55	$185.50
Purchase #2	$36.79	5.635%	$38.8631	$38.86	$38.85	$38.90
Purchase #3	$189.93	10.544%	$209.9562	$209.96	$209.95	$210.00
Purchase #4	$111.34	10.592%	$123.1331	$123.13	$123.15	$123.10
Purchase #5	$193.25	3.736%	$200.4698	$200.47	$200.45	$200.50
Purchase #6	$41.66	10.527%	$46.0455	$46.05	$46.05	$46.00
Purchase #7	$58.86	5.788%	$62.2668	$62.27	$62.25	$62.30
7 purchase totals =	$809.79		$866.2685	$866.27	$866.25	$866.30