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 $94.60   13.368%   $107.2461   $107.25   $107.25   $107.20  
  Purchase #2 $76.71   5.387%   $80.8424   $80.84   $80.85   $80.80  
  Purchase #3 $73.66   12.341%   $82.7504   $82.75   $82.75   $82.80  
  Purchase #4 $172.94   8.329%   $187.3442   $187.34   $187.35   $187.30  
  Purchase #5 $175.44   12.645%   $197.6244   $197.62   $197.60   $197.60  
  Purchase #6 $249.43   10.347%   $275.2385   $275.24   $275.25   $275.20  
  Purchase #7 $218.45   9.270%   $238.7003   $238.70   $238.70   $238.70  
  7 purchase totals = $1,061.23       $1,169.7463   $1,169.74   $1,169.75   $1,169.60