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	$246.52	8.746%	$268.0806	$268.08	$268.10	$268.10
Purchase #2	$102.36	6.421%	$108.9325	$108.93	$108.95	$108.90
Purchase #3	$72.67	5.570%	$76.7177	$76.72	$76.70	$76.70
Purchase #4	$100.99	4.434%	$105.4679	$105.47	$105.45	$105.50
Purchase #5	$66.50	8.465%	$72.1292	$72.13	$72.15	$72.10
Purchase #6	$235.59	4.799%	$246.896	$246.90	$246.90	$246.90
Purchase #7	$208.44	12.131%	$233.7259	$233.73	$233.75	$233.70
7 purchase totals =	$1,033.07		$1,111.9498	$1,111.96	$1,112.00	$1,111.90