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 $207.63   8.273%   $224.8072   $224.81   $224.80   $224.80  
  Purchase #2 $226.79   7.231%   $243.1892   $243.19   $243.20   $243.20  
  Purchase #3 $67.35   8.350%   $72.9737   $72.97   $72.95   $73.00  
  Purchase #4 $61.53   4.325%   $64.1912   $64.19   $64.20   $64.20  
  Purchase #5 $186.94   7.833%   $201.583   $201.58   $201.60   $201.60  
  Purchase #6 $56.36   4.593%   $58.9486   $58.95   $58.95   $58.90  
  Purchase #7 $225.28   8.775%   $245.0483   $245.05   $245.05   $245.00  
  7 purchase totals = $1,031.88       $1,110.7412   $1,110.74   $1,110.75   $1,110.70