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 $182.44   12.181%   $204.663   $204.66   $204.65   $204.70  
  Purchase #2 $156.27   9.855%   $171.6704   $171.67   $171.65   $171.70  
  Purchase #3 $185.84   7.587%   $199.9397   $199.94   $199.95   $199.90  
  Purchase #4 $155.71   3.831%   $161.6753   $161.68   $161.70   $161.70  
  Purchase #5 $60.98   11.132%   $67.7683   $67.77   $67.75   $67.80  
  Purchase #6 $234.84   13.777%   $267.1939   $267.19   $267.20   $267.20  
  Purchase #7 $107.58   13.358%   $121.9505   $121.95   $121.95   $122.00  
  7 purchase totals = $1,083.66       $1,194.8611   $1,194.86   $1,194.85   $1,195.00