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 $59.35   4.398%   $61.9602   $61.96   $61.95   $62.00  
  Purchase #2 $187.64   8.440%   $203.4768   $203.48   $203.50   $203.50  
  Purchase #3 $89.78   11.712%   $100.295   $100.30   $100.30   $100.30  
  Purchase #4 $134.50   11.247%   $149.6272   $149.63   $149.65   $149.60  
  Purchase #5 $98.89   5.873%   $104.6978   $104.70   $104.70   $104.70  
  Purchase #6 $172.71   12.708%   $194.658   $194.66   $194.65   $194.70  
  Purchase #7 $238.89   7.834%   $257.6046   $257.60   $257.60   $257.60  
  7 purchase totals = $981.76       $1,072.3196   $1,072.33   $1,072.35   $1,072.40