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 $118.76   12.873%   $134.048   $134.05   $134.05   $134.00  
  Purchase #2 $195.47   7.601%   $210.3277   $210.33   $210.35   $210.30  
  Purchase #3 $192.64   12.134%   $216.0149   $216.01   $216.00   $216.00  
  Purchase #4 $27.76   13.400%   $31.4798   $31.48   $31.50   $31.50  
  Purchase #5 $191.66   7.628%   $206.2798   $206.28   $206.30   $206.30  
  Purchase #6 $40.37   6.589%   $43.03   $43.03   $43.05   $43.00  
  Purchase #7 $85.37   10.794%   $94.5848   $94.58   $94.60   $94.60  
  7 purchase totals = $852.03       $935.7650   $935.76   $935.85   $935.70