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 $32.84   7.808%   $35.4041   $35.40   $35.40   $35.40  
  Purchase #2 $184.46   10.411%   $203.6641   $203.66   $203.65   $203.70  
  Purchase #3 $103.26   8.713%   $112.257   $112.26   $112.25   $112.30  
  Purchase #4 $146.75   6.212%   $155.8661   $155.87   $155.85   $155.90  
  Purchase #5 $249.26   10.818%   $276.2249   $276.22   $276.20   $276.20  
  Purchase #6 $87.56   8.347%   $94.8686   $94.87   $94.85   $94.90  
  Purchase #7 $57.86   8.247%   $62.6317   $62.63   $62.65   $62.60  
  7 purchase totals = $861.99       $940.9165   $940.91   $940.85   $941.00