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 $174.88   11.796%   $195.5088   $195.51   $195.50   $195.50  
  Purchase #2 $219.50   10.541%   $242.6375   $242.64   $242.65   $242.60  
  Purchase #3 $5.45   11.234%   $6.0623   $6.06   $6.05   $6.10  
  Purchase #4 $163.76   9.838%   $179.8707   $179.87   $179.85   $179.90  
  Purchase #5 $13.44   11.776%   $15.0227   $15.02   $15.00   $15.00  
  Purchase #6 $234.67   11.160%   $260.8592   $260.86   $260.85   $260.90  
  Purchase #7 $222.41   10.862%   $246.5682   $246.57   $246.55   $246.60  
  7 purchase totals = $1,034.11       $1,146.5294   $1,146.53   $1,146.45   $1,146.60