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 $204.67   7.246%   $219.5004   $219.50   $219.50   $219.50  
  Purchase #2 $55.88   11.292%   $62.19   $62.19   $62.20   $62.20  
  Purchase #3 $190.59   5.525%   $201.1201   $201.12   $201.10   $201.10  
  Purchase #4 $175.39   10.468%   $193.7498   $193.75   $193.75   $193.70  
  Purchase #5 $170.55   7.280%   $182.966   $182.97   $182.95   $183.00  
  Purchase #6 $44.96   7.566%   $48.3617   $48.36   $48.35   $48.40  
  Purchase #7 $135.39   12.269%   $152.001   $152.00   $152.00   $152.00  
  7 purchase totals = $977.43       $1,059.8890   $1,059.89   $1,059.85   $1,059.90