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	$243.48	5.203%	$256.1483	$256.15	$256.15	$256.10
Purchase #2	$200.65	3.659%	$207.9918	$207.99	$208.00	$208.00
Purchase #3	$18.63	12.145%	$20.8926	$20.89	$20.90	$20.90
Purchase #4	$208.91	4.593%	$218.5052	$218.51	$218.50	$218.50
Purchase #5	$173.50	9.668%	$190.274	$190.27	$190.25	$190.30
Purchase #6	$207.44	7.458%	$222.9109	$222.91	$222.90	$222.90
Purchase #7	$126.74	7.786%	$136.608	$136.61	$136.60	$136.60
7 purchase totals =	$1,179.35		$1,253.3308	$1,253.33	$1,253.30	$1,253.30