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 $68.45   9.525%   $74.9699   $74.97   $74.95   $75.00  
  Purchase #2 $198.41   9.669%   $217.5943   $217.59   $217.60   $217.60  
  Purchase #3 $125.84   7.614%   $135.4215   $135.42   $135.40   $135.40  
  Purchase #4 $178.40   13.678%   $202.8016   $202.80   $202.80   $202.80  
  Purchase #5 $74.88   12.712%   $84.3987   $84.40   $84.40   $84.40  
  Purchase #6 $115.29   5.860%   $122.046   $122.05   $122.05   $122.00  
  Purchase #7 $204.89   5.327%   $215.8045   $215.80   $215.80   $215.80  
  7 purchase totals = $966.16       $1,053.0365   $1,053.03   $1,053.00   $1,053.00