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	$20.45	10.734%	$22.6451	$22.65	$22.65	$22.60
Purchase #2	$132.52	7.799%	$142.8552	$142.86	$142.85	$142.90
Purchase #3	$83.26	7.447%	$89.4604	$89.46	$89.45	$89.50
Purchase #4	$89.82	13.588%	$102.0247	$102.02	$102.00	$102.00
Purchase #5	$240.63	8.303%	$260.6095	$260.61	$260.60	$260.60
Purchase #6	$243.50	3.448%	$251.8959	$251.90	$251.90	$251.90
Purchase #7	$41.96	10.573%	$46.3964	$46.40	$46.40	$46.40
7 purchase totals =	$852.14		$915.8872	$915.90	$915.85	$915.90