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	$201.32	10.225%	$221.905	$221.91	$221.90	$221.90
Purchase #2	$76.70	7.168%	$82.1979	$82.20	$82.20	$82.20
Purchase #3	$117.62	5.337%	$123.8974	$123.90	$123.90	$123.90
Purchase #4	$177.79	10.539%	$196.5273	$196.53	$196.55	$196.50
Purchase #5	$167.36	12.648%	$188.5277	$188.53	$188.55	$188.50
Purchase #6	$169.99	3.685%	$176.2541	$176.25	$176.25	$176.30
Purchase #7	$95.30	8.360%	$103.2671	$103.27	$103.25	$103.30
7 purchase totals =	$1,006.08		$1,092.5765	$1,092.59	$1,092.60	$1,092.60