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	$154.61	5.241%	$162.7131	$162.71	$162.70	$162.70
Purchase #2	$113.94	11.664%	$127.23	$127.23	$127.25	$127.20
Purchase #3	$163.71	9.433%	$179.1528	$179.15	$179.15	$179.20
Purchase #4	$73.31	11.179%	$81.5053	$81.51	$81.50	$81.50
Purchase #5	$76.98	7.288%	$82.5903	$82.59	$82.60	$82.60
Purchase #6	$234.32	13.308%	$265.5033	$265.50	$265.50	$265.50
Purchase #7	$130.48	10.111%	$143.6728	$143.67	$143.65	$143.70
7 purchase totals =	$947.35		$1,042.3676	$1,042.36	$1,042.35	$1,042.40