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	$200.52	13.515%	$227.6203	$227.62	$227.60	$227.60
Purchase #2	$193.82	3.362%	$200.3362	$200.34	$200.35	$200.30
Purchase #3	$236.37	8.274%	$255.9273	$255.93	$255.95	$255.90
Purchase #4	$50.89	4.823%	$53.3444	$53.34	$53.35	$53.30
Purchase #5	$125.34	3.357%	$129.5477	$129.55	$129.55	$129.50
Purchase #6	$155.65	11.834%	$174.0696	$174.07	$174.05	$174.10
Purchase #7	$30.82	3.565%	$31.9187	$31.92	$31.90	$31.90
7 purchase totals =	$993.41		$1,072.7642	$1,072.77	$1,072.75	$1,072.60