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 $188.27   8.149%   $203.6121   $203.61   $203.60   $203.60  
  Purchase #2 $10.95   6.406%   $11.6515   $11.65   $11.65   $11.70  
  Purchase #3 $47.53   8.844%   $51.7336   $51.73   $51.75   $51.70  
  Purchase #4 $181.49   6.188%   $192.7206   $192.72   $192.70   $192.70  
  Purchase #5 $228.75   9.258%   $249.9277   $249.93   $249.95   $249.90  
  Purchase #6 $83.91   13.403%   $95.1565   $95.16   $95.15   $95.20  
  Purchase #7 $242.66   8.740%   $263.8685   $263.87   $263.85   $263.90  
  7 purchase totals = $983.56       $1,068.6705   $1,068.67   $1,068.65   $1,068.70