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 $58.44   6.533%   $62.2579   $62.26   $62.25   $62.30  
  Purchase #2 $237.57   3.666%   $246.2793   $246.28   $246.30   $246.30  
  Purchase #3 $184.44   9.123%   $201.2665   $201.27   $201.25   $201.30  
  Purchase #4 $179.83   7.453%   $193.2327   $193.23   $193.25   $193.20  
  Purchase #5 $94.57   3.857%   $98.2176   $98.22   $98.20   $98.20  
  Purchase #6 $25.37   6.279%   $26.963   $26.96   $26.95   $27.00  
  Purchase #7 $22.42   7.770%   $24.162   $24.16   $24.15   $24.20  
  7 purchase totals = $802.64       $852.3790   $852.38   $852.35   $852.50