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	$171.97	10.549%	$190.1111	$190.11	$190.10	$190.10
Purchase #2	$192.37	12.404%	$216.2316	$216.23	$216.25	$216.20
Purchase #3	$237.45	7.641%	$255.5936	$255.59	$255.60	$255.60
Purchase #4	$27.66	6.381%	$29.425	$29.43	$29.45	$29.40
Purchase #5	$103.26	9.787%	$113.3661	$113.37	$113.35	$113.40
Purchase #6	$178.27	10.295%	$196.6229	$196.62	$196.60	$196.60
Purchase #7	$194.48	10.806%	$215.4955	$215.50	$215.50	$215.50
7 purchase totals =	$1,105.46		$1,216.8458	$1,216.85	$1,216.85	$1,216.80