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	$64.36	8.186%	$69.6285	$69.63	$69.65	$69.60
Purchase #2	$82.92	8.416%	$89.8985	$89.90	$89.90	$89.90
Purchase #3	$144.47	13.741%	$164.3216	$164.32	$164.30	$164.30
Purchase #4	$234.88	13.501%	$266.5911	$266.59	$266.60	$266.60
Purchase #5	$96.47	3.643%	$99.9844	$99.98	$100.00	$100.00
Purchase #6	$46.76	9.120%	$51.0245	$51.02	$51.00	$51.00
Purchase #7	$141.43	13.524%	$160.557	$160.56	$160.55	$160.60
7 purchase totals =	$811.29		$902.0056	$902.00	$902.00	$902.00