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 $41.36   12.859%   $46.6785   $46.68   $46.70   $46.70  
  Purchase #2 $198.90   3.408%   $205.6785   $205.68   $205.70   $205.70  
  Purchase #3 $68.33   4.636%   $71.4978   $71.50   $71.50   $71.50  
  Purchase #4 $170.41   4.819%   $178.6221   $178.62   $178.60   $178.60  
  Purchase #5 $212.81   11.622%   $237.5428   $237.54   $237.55   $237.50  
  Purchase #6 $66.33   13.393%   $75.2136   $75.21   $75.20   $75.20  
  Purchase #7 $9.75   9.420%   $10.6685   $10.67   $10.65   $10.70  
  7 purchase totals = $767.89       $825.9018   $825.90   $825.90   $825.90