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 $72.39   6.850%   $77.3487   $77.35   $77.35   $77.30  
  Purchase #2 $131.35   6.847%   $140.3435   $140.34   $140.35   $140.30  
  Purchase #3 $219.45   6.145%   $232.9352   $232.94   $232.95   $232.90  
  Purchase #4 $235.38   13.623%   $267.4458   $267.45   $267.45   $267.40  
  Purchase #5 $95.97   8.571%   $104.1956   $104.20   $104.20   $104.20  
  Purchase #6 $112.82   9.844%   $123.926   $123.93   $123.95   $123.90  
  Purchase #7 $202.63   5.663%   $214.1049   $214.10   $214.10   $214.10  
  7 purchase totals = $1,069.99       $1,160.2997   $1,160.31   $1,160.35   $1,160.10