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 $47.64   9.530%   $52.1801   $52.18   $52.20   $52.20  
  Purchase #2 $232.56   3.784%   $241.3601   $241.36   $241.35   $241.40  
  Purchase #3 $156.38   11.682%   $174.6483   $174.65   $174.65   $174.60  
  Purchase #4 $233.54   7.816%   $251.7935   $251.79   $251.80   $251.80  
  Purchase #5 $146.75   9.822%   $161.1638   $161.16   $161.15   $161.20  
  Purchase #6 $37.65   3.576%   $38.9964   $39.00   $39.00   $39.00  
  Purchase #7 $187.76   13.872%   $213.8061   $213.81   $213.80   $213.80  
  7 purchase totals = $1,042.28       $1,133.9483   $1,133.95   $1,133.95   $1,134.00