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 $44.34   7.544%   $47.685   $47.69   $47.70   $47.70  
  Purchase #2 $88.61   6.292%   $94.1853   $94.19   $94.20   $94.20  
  Purchase #3 $56.47   6.806%   $60.3133   $60.31   $60.30   $60.30  
  Purchase #4 $175.59   5.117%   $184.5749   $184.57   $184.55   $184.60  
  Purchase #5 $182.34   6.704%   $194.5641   $194.56   $194.55   $194.60  
  Purchase #6 $195.83   9.167%   $213.7817   $213.78   $213.80   $213.80  
  Purchase #7 $197.25   7.796%   $212.6276   $212.63   $212.65   $212.60  
  7 purchase totals = $940.43       $1,007.7319   $1,007.73   $1,007.75   $1,007.80