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 $127.96   5.248%   $134.6753   $134.68   $134.70   $134.70  
  Purchase #2 $206.62   6.408%   $219.8602   $219.86   $219.85   $219.90  
  Purchase #3 $216.64   5.199%   $227.9031   $227.90   $227.90   $227.90  
  Purchase #4 $83.44   7.278%   $89.5128   $89.51   $89.50   $89.50  
  Purchase #5 $133.41   5.374%   $140.5795   $140.58   $140.60   $140.60  
  Purchase #6 $117.88   6.798%   $125.8935   $125.89   $125.90   $125.90  
  Purchase #7 $8.49   12.172%   $9.5234   $9.52   $9.50   $9.50  
  7 purchase totals = $894.44       $947.9478   $947.94   $947.95   $948.00