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 $116.60   7.821%   $125.7193   $125.72   $125.70   $125.70  
  Purchase #2 $77.87   8.395%   $84.4072   $84.41   $84.40   $84.40  
  Purchase #3 $216.96   5.446%   $228.7756   $228.78   $228.80   $228.80  
  Purchase #4 $246.41   8.640%   $267.6998   $267.70   $267.70   $267.70  
  Purchase #5 $225.68   7.706%   $243.0709   $243.07   $243.05   $243.10  
  Purchase #6 $24.79   11.202%   $27.567   $27.57   $27.55   $27.60  
  Purchase #7 $205.61   9.636%   $225.4226   $225.42   $225.40   $225.40  
  7 purchase totals = $1,113.92       $1,202.6624   $1,202.67   $1,202.60   $1,202.70