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 $93.77   13.243%   $106.188   $106.19   $106.20   $106.20  
  Purchase #2 $93.38   5.197%   $98.233   $98.23   $98.25   $98.20  
  Purchase #3 $218.27   3.392%   $225.6737   $225.67   $225.65   $225.70  
  Purchase #4 $83.49   7.390%   $89.6599   $89.66   $89.65   $89.70  
  Purchase #5 $208.60   11.499%   $232.5869   $232.59   $232.60   $232.60  
  Purchase #6 $151.96   5.227%   $159.9029   $159.90   $159.90   $159.90  
  Purchase #7 $175.61   9.240%   $191.8364   $191.84   $191.85   $191.80  
  7 purchase totals = $1,025.08       $1,104.0808   $1,104.08   $1,104.10   $1,104.10