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 $53.88   3.831%   $55.9441   $55.94   $55.95   $55.90  
  Purchase #2 $167.98   8.472%   $182.2113   $182.21   $182.20   $182.20  
  Purchase #3 $196.82   3.734%   $204.1693   $204.17   $204.15   $204.20  
  Purchase #4 $177.73   4.800%   $186.261   $186.26   $186.25   $186.30  
  Purchase #5 $17.57   6.203%   $18.6599   $18.66   $18.65   $18.70  
  Purchase #6 $139.51   3.677%   $144.6398   $144.64   $144.65   $144.60  
  Purchase #7 $207.59   5.501%   $219.0095   $219.01   $219.00   $219.00  
  7 purchase totals = $961.08       $1,010.8949   $1,010.89   $1,010.85   $1,010.90