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 $182.57   8.319%   $197.758   $197.76   $197.75   $197.80  
  Purchase #2 $131.49   7.774%   $141.712   $141.71   $141.70   $141.70  
  Purchase #3 $96.54   10.331%   $106.5135   $106.51   $106.50   $106.50  
  Purchase #4 $75.43   12.776%   $85.0669   $85.07   $85.05   $85.10  
  Purchase #5 $184.58   4.665%   $193.1907   $193.19   $193.20   $193.20  
  Purchase #6 $9.79   8.703%   $10.642   $10.64   $10.65   $10.60  
  Purchase #7 $146.48   9.632%   $160.589   $160.59   $160.60   $160.60  
  7 purchase totals = $826.88       $895.4721   $895.47   $895.45   $895.50