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	$98.85	9.847%	$108.5838	$108.58	$108.60	$108.60
Purchase #2	$159.60	5.602%	$168.5408	$168.54	$168.55	$168.50
Purchase #3	$234.29	5.299%	$246.705	$246.71	$246.70	$246.70
Purchase #4	$149.34	10.214%	$164.5936	$164.59	$164.60	$164.60
Purchase #5	$216.89	13.343%	$245.8296	$245.83	$245.85	$245.80
Purchase #6	$29.60	6.555%	$31.5403	$31.54	$31.55	$31.50
Purchase #7	$141.60	6.489%	$150.7884	$150.79	$150.80	$150.80
7 purchase totals =	$1,030.17		$1,116.5815	$1,116.58	$1,116.65	$1,116.50