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	$241.83	13.219%	$273.7975	$273.80	$273.80	$273.80
Purchase #2	$91.85	11.644%	$102.545	$102.55	$102.55	$102.50
Purchase #3	$197.43	7.440%	$212.1188	$212.12	$212.10	$212.10
Purchase #4	$125.50	12.394%	$141.0545	$141.05	$141.05	$141.10
Purchase #5	$240.98	4.354%	$251.4723	$251.47	$251.45	$251.50
Purchase #6	$26.66	12.123%	$29.892	$29.89	$29.90	$29.90
Purchase #7	$91.82	3.464%	$95.0006	$95.00	$95.00	$95.00
7 purchase totals =	$1,016.07		$1,105.8807	$1,105.88	$1,105.85	$1,105.90