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 $183.54   11.622%   $204.871   $204.87   $204.85   $204.90  
  Purchase #2 $9.27   12.347%   $10.4146   $10.41   $10.40   $10.40  
  Purchase #3 $194.91   6.702%   $207.9729   $207.97   $207.95   $208.00  
  Purchase #4 $119.45   11.760%   $133.4973   $133.50   $133.50   $133.50  
  Purchase #5 $225.53   9.589%   $247.1561   $247.16   $247.15   $247.20  
  Purchase #6 $156.27   6.227%   $166.0009   $166.00   $166.00   $166.00  
  Purchase #7 $206.59   12.323%   $232.0481   $232.05   $232.05   $232.00  
  7 purchase totals = $1,095.56       $1,201.9609   $1,201.96   $1,201.90   $1,202.00