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 $186.71   9.330%   $204.13   $204.13   $204.15   $204.10  
  Purchase #2 $225.87   4.203%   $235.3633   $235.36   $235.35   $235.40  
  Purchase #3 $91.58   6.256%   $97.3092   $97.31   $97.30   $97.30  
  Purchase #4 $157.93   3.628%   $163.6597   $163.66   $163.65   $163.70  
  Purchase #5 $111.99   6.214%   $118.9491   $118.95   $118.95   $118.90  
  Purchase #6 $80.27   13.668%   $91.2413   $91.24   $91.25   $91.20  
  Purchase #7 $41.72   6.250%   $44.3275   $44.33   $44.35   $44.30  
  7 purchase totals = $896.07       $954.9801   $954.98   $955.00   $954.90