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 $92.45   3.143%   $95.3557   $95.36   $95.35   $95.40  
  Purchase #2 $86.96   7.337%   $93.3403   $93.34   $93.35   $93.30  
  Purchase #3 $148.80   5.443%   $156.8992   $156.90   $156.90   $156.90  
  Purchase #4 $129.90   7.357%   $139.4567   $139.46   $139.45   $139.50  
  Purchase #5 $101.29   12.278%   $113.7264   $113.73   $113.75   $113.70  
  Purchase #6 $60.33   12.654%   $67.9642   $67.96   $67.95   $68.00  
  Purchase #7 $207.68   11.150%   $230.8363   $230.84   $230.85   $230.80  
  7 purchase totals = $827.41       $897.5788   $897.59   $897.60   $897.60