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 $202.38   11.126%   $224.8968   $224.90   $224.90   $224.90  
  Purchase #2 $196.39   13.526%   $222.9537   $222.95   $222.95   $223.00  
  Purchase #3 $98.73   3.415%   $102.1016   $102.10   $102.10   $102.10  
  Purchase #4 $166.61   11.654%   $186.0267   $186.03   $186.05   $186.00  
  Purchase #5 $200.42   4.336%   $209.1102   $209.11   $209.10   $209.10  
  Purchase #6 $118.85   13.837%   $135.2953   $135.30   $135.30   $135.30  
  Purchase #7 $173.88   4.801%   $182.228   $182.23   $182.25   $182.20  
  7 purchase totals = $1,157.26       $1,262.6123   $1,262.62   $1,262.65   $1,262.60