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	$214.78	9.331%	$234.8211	$234.82	$234.80	$234.80
Purchase #2	$45.45	10.718%	$50.3213	$50.32	$50.30	$50.30
Purchase #3	$248.52	9.312%	$271.6622	$271.66	$271.65	$271.70
Purchase #4	$83.62	7.212%	$89.6507	$89.65	$89.65	$89.70
Purchase #5	$242.54	5.353%	$255.5232	$255.52	$255.50	$255.50
Purchase #6	$60.40	5.800%	$63.9032	$63.90	$63.90	$63.90
Purchase #7	$113.89	11.390%	$126.8621	$126.86	$126.85	$126.90
7 purchase totals =	$1,009.20		$1,092.7438	$1,092.73	$1,092.65	$1,092.80