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 $183.82   5.557%   $194.0349   $194.03   $194.05   $194.00  
  Purchase #2 $246.65   6.502%   $262.6872   $262.69   $262.70   $262.70  
  Purchase #3 $239.58   10.614%   $265.009   $265.01   $265.00   $265.00  
  Purchase #4 $212.35   5.417%   $223.853   $223.85   $223.85   $223.90  
  Purchase #5 $140.44   12.682%   $158.2506   $158.25   $158.25   $158.30  
  Purchase #6 $177.46   6.470%   $188.9417   $188.94   $188.95   $188.90  
  Purchase #7 $85.32   8.351%   $92.4451   $92.45   $92.45   $92.40  
  7 purchase totals = $1,285.62       $1,385.2215   $1,385.22   $1,385.25   $1,385.20