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 $54.95   6.229%   $58.3728   $58.37   $58.35   $58.40  
  Purchase #2 $200.66   5.744%   $212.1859   $212.19   $212.20   $212.20  
  Purchase #3 $105.90   7.220%   $113.546   $113.55   $113.55   $113.50  
  Purchase #4 $196.81   3.614%   $203.9227   $203.92   $203.90   $203.90  
  Purchase #5 $191.44   9.722%   $210.0518   $210.05   $210.05   $210.10  
  Purchase #6 $169.46   8.147%   $183.2659   $183.27   $183.25   $183.30  
  Purchase #7 $184.94   3.148%   $190.7619   $190.76   $190.75   $190.80  
  7 purchase totals = $1,104.16       $1,172.1070   $1,172.11   $1,172.05   $1,172.20