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 $181.61   8.532%   $197.105   $197.11   $197.10   $197.10  
  Purchase #2 $33.83   11.867%   $37.8446   $37.84   $37.85   $37.80  
  Purchase #3 $163.88   11.421%   $182.5967   $182.60   $182.60   $182.60  
  Purchase #4 $78.84   8.194%   $85.3001   $85.30   $85.30   $85.30  
  Purchase #5 $83.42   13.112%   $94.358   $94.36   $94.35   $94.40  
  Purchase #6 $173.72   6.355%   $184.7599   $184.76   $184.75   $184.80  
  Purchase #7 $102.30   10.207%   $112.7418   $112.74   $112.75   $112.70  
  7 purchase totals = $817.60       $894.7061   $894.71   $894.70   $894.70