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 $195.74   5.671%   $206.8404   $206.84   $206.85   $206.80  
  Purchase #2 $197.93   4.526%   $206.8883   $206.89   $206.90   $206.90  
  Purchase #3 $95.76   13.770%   $108.9462   $108.95   $108.95   $108.90  
  Purchase #4 $22.52   9.485%   $24.656   $24.66   $24.65   $24.70  
  Purchase #5 $153.84   13.529%   $174.653   $174.65   $174.65   $174.70  
  Purchase #6 $159.34   4.285%   $166.1677   $166.17   $166.15   $166.20  
  Purchase #7 $53.60   5.391%   $56.4896   $56.49   $56.50   $56.50  
  7 purchase totals = $878.73       $944.6412   $944.65   $944.65   $944.70