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 $225.86   8.473%   $244.9971   $245.00   $245.00   $245.00  
  Purchase #2 $53.80   7.131%   $57.6365   $57.64   $57.65   $57.60  
  Purchase #3 $178.42   12.796%   $201.2506   $201.25   $201.25   $201.30  
  Purchase #4 $164.88   8.370%   $178.6805   $178.68   $178.70   $178.70  
  Purchase #5 $54.28   8.427%   $58.8542   $58.85   $58.85   $58.90  
  Purchase #6 $68.94   9.837%   $75.7216   $75.72   $75.70   $75.70  
  Purchase #7 $203.98   13.134%   $230.7707   $230.77   $230.75   $230.80  
  7 purchase totals = $950.16       $1,047.9112   $1,047.91   $1,047.90   $1,048.00