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 $212.31   13.611%   $241.2075   $241.21   $241.20   $241.20  
  Purchase #2 $235.73   4.461%   $246.2459   $246.25   $246.25   $246.20  
  Purchase #3 $25.97   3.858%   $26.9719   $26.97   $26.95   $27.00  
  Purchase #4 $41.57   7.702%   $44.7717   $44.77   $44.75   $44.80  
  Purchase #5 $230.63   9.639%   $252.8604   $252.86   $252.85   $252.90  
  Purchase #6 $55.38   7.761%   $59.678   $59.68   $59.70   $59.70  
  Purchase #7 $218.88   6.134%   $232.3061   $232.31   $232.30   $232.30  
  7 purchase totals = $1,020.47       $1,104.0415   $1,104.05   $1,104.00   $1,104.10