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 $181.51   8.232%   $196.4519   $196.45   $196.45   $196.50  
  Purchase #2 $192.47   7.218%   $206.3625   $206.36   $206.35   $206.40  
  Purchase #3 $41.63   11.485%   $46.4112   $46.41   $46.40   $46.40  
  Purchase #4 $211.90   8.336%   $229.564   $229.56   $229.55   $229.60  
  Purchase #5 $69.34   8.315%   $75.1056   $75.11   $75.10   $75.10  
  Purchase #6 $222.68   11.387%   $248.0366   $248.04   $248.05   $248.00  
  Purchase #7 $231.80   7.643%   $249.5165   $249.52   $249.50   $249.50  
  7 purchase totals = $1,151.33       $1,251.4483   $1,251.45   $1,251.40   $1,251.50