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 $84.47   12.539%   $95.0617   $95.06   $95.05   $95.10  
  Purchase #2 $167.84   3.650%   $173.9662   $173.97   $173.95   $174.00  
  Purchase #3 $19.72   3.542%   $20.4185   $20.42   $20.40   $20.40  
  Purchase #4 $193.49   8.490%   $209.9173   $209.92   $209.90   $209.90  
  Purchase #5 $153.40   10.314%   $169.2217   $169.22   $169.20   $169.20  
  Purchase #6 $198.99   11.280%   $221.4361   $221.44   $221.45   $221.40  
  Purchase #7 $156.54   3.499%   $162.0173   $162.02   $162.00   $162.00  
  7 purchase totals = $974.45       $1,052.0388   $1,052.05   $1,051.95   $1,052.00