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	$241.45	11.427%	$269.0405	$269.04	$269.05	$269.00
Purchase #2	$217.83	13.566%	$247.3808	$247.38	$247.40	$247.40
Purchase #3	$122.87	12.201%	$137.8614	$137.86	$137.85	$137.90
Purchase #4	$150.74	5.561%	$159.1227	$159.12	$159.10	$159.10
Purchase #5	$204.92	12.801%	$231.1518	$231.15	$231.15	$231.20
Purchase #6	$47.46	10.703%	$52.5396	$52.54	$52.55	$52.50
Purchase #7	$164.55	4.854%	$172.5373	$172.54	$172.55	$172.50
7 purchase totals =	$1,149.82		$1,269.6341	$1,269.63	$1,269.65	$1,269.60