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 $93.87   11.691%   $104.8443   $104.84   $104.85   $104.80  
  Purchase #2 $207.98   13.166%   $235.3626   $235.36   $235.35   $235.40  
  Purchase #3 $223.67   10.220%   $246.5291   $246.53   $246.55   $246.50  
  Purchase #4 $181.31   4.842%   $190.089   $190.09   $190.10   $190.10  
  Purchase #5 $32.95   7.269%   $35.3451   $35.35   $35.35   $35.30  
  Purchase #6 $206.33   4.615%   $215.8521   $215.85   $215.85   $215.90  
  Purchase #7 $149.57   8.828%   $162.774   $162.77   $162.75   $162.80  
  7 purchase totals = $1,095.68       $1,190.7962   $1,190.79   $1,190.80   $1,190.80