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 $195.32   5.445%   $205.9552   $205.96   $205.95   $206.00  
  Purchase #2 $22.38   7.151%   $23.9804   $23.98   $24.00   $24.00  
  Purchase #3 $76.48   7.254%   $82.0279   $82.03   $82.05   $82.00  
  Purchase #4 $82.28   9.319%   $89.9477   $89.95   $89.95   $89.90  
  Purchase #5 $31.37   3.740%   $32.5432   $32.54   $32.55   $32.50  
  Purchase #6 $206.97   8.775%   $225.1316   $225.13   $225.15   $225.10  
  Purchase #7 $202.50   6.673%   $216.0128   $216.01   $216.00   $216.00  
  7 purchase totals = $817.30       $875.5988   $875.60   $875.65   $875.50