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 $191.29   3.474%   $197.9354   $197.94   $197.95   $197.90  
  Purchase #2 $75.45   8.269%   $81.689   $81.69   $81.70   $81.70  
  Purchase #3 $85.74   10.758%   $94.9639   $94.96   $94.95   $95.00  
  Purchase #4 $62.90   4.227%   $65.5588   $65.56   $65.55   $65.60  
  Purchase #5 $233.75   4.849%   $245.0845   $245.08   $245.10   $245.10  
  Purchase #6 $68.97   8.229%   $74.6455   $74.65   $74.65   $74.60  
  Purchase #7 $250.59   9.214%   $273.6794   $273.68   $273.70   $273.70  
  7 purchase totals = $968.69       $1,033.5565   $1,033.56   $1,033.60   $1,033.60