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 $244.81   8.103%   $264.647   $264.65   $264.65   $264.60  
  Purchase #2 $55.53   8.424%   $60.2078   $60.21   $60.20   $60.20  
  Purchase #3 $194.98   7.440%   $209.4865   $209.49   $209.50   $209.50  
  Purchase #4 $63.86   5.121%   $67.1303   $67.13   $67.15   $67.10  
  Purchase #5 $202.29   4.161%   $210.7073   $210.71   $210.70   $210.70  
  Purchase #6 $84.34   12.710%   $95.0596   $95.06   $95.05   $95.10  
  Purchase #7 $248.88   7.285%   $267.0109   $267.01   $267.00   $267.00  
  7 purchase totals = $1,094.69       $1,174.2494   $1,174.26   $1,174.25   $1,174.20