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	$134.99	7.170%	$144.6688	$144.67	$144.65	$144.70
Purchase #2	$243.50	6.173%	$258.5313	$258.53	$258.55	$258.50
Purchase #3	$54.32	8.856%	$59.1306	$59.13	$59.15	$59.10
Purchase #4	$9.83	6.664%	$10.4851	$10.49	$10.50	$10.50
Purchase #5	$54.58	12.826%	$61.5804	$61.58	$61.60	$61.60
Purchase #6	$125.63	11.287%	$139.8099	$139.81	$139.80	$139.80
Purchase #7	$237.94	5.692%	$251.4835	$251.48	$251.50	$251.50
7 purchase totals =	$860.79		$925.6896	$925.69	$925.75	$925.70