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	$217.78	7.687%	$234.5207	$234.52	$234.50	$234.50
Purchase #2	$216.44	4.443%	$226.0564	$226.06	$226.05	$226.10
Purchase #3	$89.96	13.823%	$102.3952	$102.40	$102.40	$102.40
Purchase #4	$148.68	13.295%	$168.447	$168.45	$168.45	$168.40
Purchase #5	$183.91	5.176%	$193.4292	$193.43	$193.45	$193.40
Purchase #6	$13.98	13.134%	$15.8161	$15.82	$15.80	$15.80
Purchase #7	$130.78	11.266%	$145.5137	$145.51	$145.50	$145.50
7 purchase totals =	$1,001.53		$1,086.1783	$1,086.19	$1,086.15	$1,086.10