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 $76.27   7.782%   $82.2053   $82.21   $82.20   $82.20  
  Purchase #2 $226.55   13.250%   $256.5679   $256.57   $256.55   $256.60  
  Purchase #3 $241.54   9.425%   $264.3051   $264.31   $264.30   $264.30  
  Purchase #4 $221.64   3.604%   $229.6279   $229.63   $229.65   $229.60  
  Purchase #5 $208.59   12.851%   $235.3959   $235.40   $235.40   $235.40  
  Purchase #6 $153.51   13.785%   $174.6714   $174.67   $174.65   $174.70  
  Purchase #7 $75.64   9.490%   $82.8182   $82.82   $82.80   $82.80  
  7 purchase totals = $1,203.74       $1,325.5917   $1,325.61   $1,325.55   $1,325.60