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	$189.29	3.629%	$196.1593	$196.16	$196.15	$196.20
Purchase #2	$182.32	10.717%	$201.8592	$201.86	$201.85	$201.90
Purchase #3	$104.68	8.333%	$113.403	$113.40	$113.40	$113.40
Purchase #4	$76.52	10.468%	$84.5301	$84.53	$84.55	$84.50
Purchase #5	$52.43	13.370%	$59.4399	$59.44	$59.45	$59.40
Purchase #6	$209.58	7.172%	$224.6111	$224.61	$224.60	$224.60
Purchase #7	$139.43	10.771%	$154.448	$154.45	$154.45	$154.40
7 purchase totals =	$954.25		$1,034.4506	$1,034.45	$1,034.45	$1,034.40