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 $44.91   10.529%   $49.6386   $49.64   $49.65   $49.60  
  Purchase #2 $88.92   5.471%   $93.7848   $93.78   $93.80   $93.80  
  Purchase #3 $166.59   11.451%   $185.6662   $185.67   $185.65   $185.70  
  Purchase #4 $227.88   8.336%   $246.8761   $246.88   $246.90   $246.90  
  Purchase #5 $221.90   8.401%   $240.5418   $240.54   $240.55   $240.50  
  Purchase #6 $163.68   6.603%   $174.4878   $174.49   $174.50   $174.50  
  Purchase #7 $61.74   12.547%   $69.4865   $69.49   $69.50   $69.50  
  7 purchase totals = $975.62       $1,060.4818   $1,060.49   $1,060.55   $1,060.50