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	$195.48	10.510%	$216.0249	$216.02	$216.00	$216.00
Purchase #2	$81.32	10.105%	$89.5374	$89.54	$89.55	$89.50
Purchase #3	$171.96	7.720%	$185.2353	$185.24	$185.25	$185.20
Purchase #4	$88.45	6.420%	$94.1285	$94.13	$94.15	$94.10
Purchase #5	$42.31	9.480%	$46.321	$46.32	$46.30	$46.30
Purchase #6	$143.74	4.420%	$150.0933	$150.09	$150.10	$150.10
Purchase #7	$176.37	7.431%	$189.4761	$189.48	$189.50	$189.50
7 purchase totals =	$899.63		$970.8165	$970.82	$970.85	$970.70