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 $88.59   7.279%   $95.0385   $95.04   $95.05   $95.00  
  Purchase #2 $38.54   4.566%   $40.2997   $40.30   $40.30   $40.30  
  Purchase #3 $217.61   5.611%   $229.8201   $229.82   $229.80   $229.80  
  Purchase #4 $59.72   7.599%   $64.2581   $64.26   $64.25   $64.30  
  Purchase #5 $17.49   13.159%   $19.7915   $19.79   $19.80   $19.80  
  Purchase #6 $152.90   12.835%   $172.5247   $172.52   $172.50   $172.50  
  Purchase #7 $234.75   8.189%   $253.9737   $253.97   $253.95   $254.00  
  7 purchase totals = $809.60       $875.7063   $875.70   $875.65   $875.70