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 $86.95   8.283%   $94.1521   $94.15   $94.15   $94.20  
  Purchase #2 $22.58   9.717%   $24.7741   $24.77   $24.75   $24.80  
  Purchase #3 $242.72   3.232%   $250.5647   $250.56   $250.55   $250.60  
  Purchase #4 $165.35   8.576%   $179.5304   $179.53   $179.55   $179.50  
  Purchase #5 $232.98   5.546%   $245.9011   $245.90   $245.90   $245.90  
  Purchase #6 $147.91   10.436%   $163.3459   $163.35   $163.35   $163.30  
  Purchase #7 $121.63   11.729%   $135.896   $135.90   $135.90   $135.90  
  7 purchase totals = $1,020.12       $1,094.1643   $1,094.16   $1,094.15   $1,094.20