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	$114.40	13.509%	$129.8543	$129.85	$129.85	$129.90
Purchase #2	$56.38	13.640%	$64.0702	$64.07	$64.05	$64.10
Purchase #3	$142.39	9.610%	$156.0737	$156.07	$156.05	$156.10
Purchase #4	$34.84	8.439%	$37.7801	$37.78	$37.80	$37.80
Purchase #5	$117.89	11.664%	$131.6407	$131.64	$131.65	$131.60
Purchase #6	$121.89	12.852%	$137.5553	$137.56	$137.55	$137.60
Purchase #7	$180.34	6.507%	$192.0747	$192.07	$192.05	$192.10
7 purchase totals =	$768.13		$849.0490	$849.04	$849.00	$849.20