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	$218.25	8.371%	$236.5197	$236.52	$236.50	$236.50
Purchase #2	$162.56	5.571%	$171.6162	$171.62	$171.60	$171.60
Purchase #3	$213.31	6.832%	$227.8833	$227.88	$227.90	$227.90
Purchase #4	$52.58	13.828%	$59.8508	$59.85	$59.85	$59.90
Purchase #5	$47.43	13.618%	$53.889	$53.89	$53.90	$53.90
Purchase #6	$38.58	12.859%	$43.541	$43.54	$43.55	$43.50
Purchase #7	$237.98	12.844%	$268.5462	$268.55	$268.55	$268.50
7 purchase totals =	$970.69		$1,061.8462	$1,061.85	$1,061.85	$1,061.80