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 $201.80   11.598%   $225.2048   $225.20   $225.20   $225.20  
  Purchase #2 $236.26   13.859%   $269.0033   $269.00   $269.00   $269.00  
  Purchase #3 $43.64   7.461%   $46.896   $46.90   $46.90   $46.90  
  Purchase #4 $99.98   8.712%   $108.6903   $108.69   $108.70   $108.70  
  Purchase #5 $53.87   3.540%   $55.777   $55.78   $55.80   $55.80  
  Purchase #6 $188.29   8.533%   $204.3568   $204.36   $204.35   $204.40  
  Purchase #7 $104.45   10.166%   $115.0684   $115.07   $115.05   $115.10  
  7 purchase totals = $928.29       $1,024.9966   $1,025.00   $1,025.00   $1,025.10