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	$155.83	13.524%	$176.9044	$176.90	$176.90	$176.90
Purchase #2	$189.92	10.111%	$209.1228	$209.12	$209.10	$209.10
Purchase #3	$42.66	13.757%	$48.5287	$48.53	$48.55	$48.50
Purchase #4	$60.54	5.379%	$63.7964	$63.80	$63.80	$63.80
Purchase #5	$102.35	7.160%	$109.6783	$109.68	$109.70	$109.70
Purchase #6	$75.70	10.653%	$83.7643	$83.76	$83.75	$83.80
Purchase #7	$89.78	5.660%	$94.8615	$94.86	$94.85	$94.90
7 purchase totals =	$716.78		$786.6564	$786.65	$786.65	$786.70