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 $163.86   6.254%   $174.1078   $174.11   $174.10   $174.10  
  Purchase #2 $155.58   10.201%   $171.4507   $171.45   $171.45   $171.50  
  Purchase #3 $244.53   6.205%   $259.7031   $259.70   $259.70   $259.70  
  Purchase #4 $182.65   7.686%   $196.6885   $196.69   $196.70   $196.70  
  Purchase #5 $56.39   9.870%   $61.9557   $61.96   $61.95   $62.00  
  Purchase #6 $145.61   12.429%   $163.7079   $163.71   $163.70   $163.70  
  Purchase #7 $82.96   5.623%   $87.6248   $87.62   $87.60   $87.60  
  7 purchase totals = $1,031.58       $1,115.2385   $1,115.24   $1,115.20   $1,115.30