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	$214.27	11.488%	$238.8853	$238.89	$238.90	$238.90
Purchase #2	$212.37	11.835%	$237.504	$237.50	$237.50	$237.50
Purchase #3	$40.62	8.465%	$44.0585	$44.06	$44.05	$44.10
Purchase #4	$244.78	13.674%	$278.2512	$278.25	$278.25	$278.30
Purchase #5	$143.44	12.159%	$160.8809	$160.88	$160.90	$160.90
Purchase #6	$59.45	5.188%	$62.5343	$62.53	$62.55	$62.50
Purchase #7	$91.77	9.355%	$100.3551	$100.36	$100.35	$100.40
7 purchase totals =	$1,006.70		$1,122.4693	$1,122.47	$1,122.50	$1,122.60