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 $87.52   8.610%   $95.0555   $95.06   $95.05   $95.10  
  Purchase #2 $123.49   13.321%   $139.9401   $139.94   $139.95   $139.90  
  Purchase #3 $43.34   4.264%   $45.188   $45.19   $45.20   $45.20  
  Purchase #4 $162.50   9.339%   $177.6759   $177.68   $177.70   $177.70  
  Purchase #5 $240.30   4.708%   $251.6133   $251.61   $251.60   $251.60  
  Purchase #6 $196.96   9.686%   $216.0375   $216.04   $216.05   $216.00  
  Purchase #7 $135.82   12.184%   $152.3683   $152.37   $152.35   $152.40  
  7 purchase totals = $989.93       $1,077.8786   $1,077.89   $1,077.90   $1,077.90