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 $76.48   8.546%   $83.016   $83.02   $83.00   $83.00  
  Purchase #2 $236.87   9.583%   $259.5693   $259.57   $259.55   $259.60  
  Purchase #3 $69.98   8.658%   $76.0389   $76.04   $76.05   $76.00  
  Purchase #4 $189.66   10.298%   $209.1912   $209.19   $209.20   $209.20  
  Purchase #5 $243.91   11.626%   $272.267   $272.27   $272.25   $272.30  
  Purchase #6 $151.46   5.807%   $160.2553   $160.26   $160.25   $160.30  
  Purchase #7 $79.26   6.810%   $84.6576   $84.66   $84.65   $84.70  
  7 purchase totals = $1,047.62       $1,144.9953   $1,145.01   $1,144.95   $1,145.10