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 $126.92   5.699%   $134.1532   $134.15   $134.15   $134.20  
  Purchase #2 $117.63   6.657%   $125.4606   $125.46   $125.45   $125.50  
  Purchase #3 $67.79   13.180%   $76.7247   $76.72   $76.70   $76.70  
  Purchase #4 $147.71   3.438%   $152.7883   $152.79   $152.80   $152.80  
  Purchase #5 $235.83   4.297%   $245.9636   $245.96   $245.95   $246.00  
  Purchase #6 $207.79   5.747%   $219.7317   $219.73   $219.75   $219.70  
  Purchase #7 $194.72   3.728%   $201.9792   $201.98   $202.00   $202.00  
  7 purchase totals = $1,098.39       $1,156.8013   $1,156.79   $1,156.80   $1,156.90