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	$84.96	7.825%	$91.6081	$91.61	$91.60	$91.60
Purchase #2	$144.79	7.405%	$155.5117	$155.51	$155.50	$155.50
Purchase #3	$142.80	9.433%	$156.2703	$156.27	$156.25	$156.30
Purchase #4	$80.52	3.419%	$83.273	$83.27	$83.25	$83.30
Purchase #5	$118.26	9.633%	$129.652	$129.65	$129.65	$129.70
Purchase #6	$200.87	6.484%	$213.8944	$213.89	$213.90	$213.90
Purchase #7	$235.61	8.273%	$255.102	$255.10	$255.10	$255.10
7 purchase totals =	$1,007.81		$1,085.3115	$1,085.30	$1,085.25	$1,085.40