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	$153.81	9.714%	$168.7511	$168.75	$168.75	$168.80
Purchase #2	$61.42	4.757%	$64.3417	$64.34	$64.35	$64.30
Purchase #3	$89.94	6.598%	$95.8742	$95.87	$95.85	$95.90
Purchase #4	$133.99	12.202%	$150.3395	$150.34	$150.35	$150.30
Purchase #5	$80.46	7.630%	$86.5991	$86.60	$86.60	$86.60
Purchase #6	$41.72	3.761%	$43.2891	$43.29	$43.30	$43.30
Purchase #7	$128.65	8.148%	$139.1324	$139.13	$139.15	$139.10
7 purchase totals =	$689.99		$748.3271	$748.32	$748.35	$748.30