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	$126.50	7.618%	$136.1368	$136.14	$136.15	$136.10
Purchase #2	$76.75	13.268%	$86.9332	$86.93	$86.95	$86.90
Purchase #3	$102.57	5.757%	$108.475	$108.48	$108.50	$108.50
Purchase #4	$174.29	7.444%	$187.2641	$187.26	$187.25	$187.30
Purchase #5	$164.52	3.493%	$170.2667	$170.27	$170.25	$170.30
Purchase #6	$217.47	7.320%	$233.3888	$233.39	$233.40	$233.40
Purchase #7	$134.70	3.400%	$139.2798	$139.28	$139.30	$139.30
7 purchase totals =	$996.80		$1,061.7444	$1,061.75	$1,061.80	$1,061.80