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	$85.96	4.512%	$89.8385	$89.84	$89.85	$89.80
Purchase #2	$214.49	13.197%	$242.7962	$242.80	$242.80	$242.80
Purchase #3	$130.88	12.256%	$146.9207	$146.92	$146.90	$146.90
Purchase #4	$134.28	7.151%	$143.8824	$143.88	$143.90	$143.90
Purchase #5	$36.49	5.268%	$38.4123	$38.41	$38.40	$38.40
Purchase #6	$69.60	3.462%	$72.0096	$72.01	$72.00	$72.00
Purchase #7	$43.65	4.448%	$45.5916	$45.59	$45.60	$45.60
7 purchase totals =	$715.35		$779.4513	$779.45	$779.45	$779.40