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 $196.95   7.555%   $211.8296   $211.83   $211.85   $211.80  
  Purchase #2 $246.77   13.742%   $280.6811   $280.68   $280.70   $280.70  
  Purchase #3 $169.85   9.712%   $186.3458   $186.35   $186.35   $186.30  
  Purchase #4 $62.81   8.628%   $68.2292   $68.23   $68.25   $68.20  
  Purchase #5 $207.47   6.466%   $220.885   $220.89   $220.90   $220.90  
  Purchase #6 $117.54   5.772%   $124.3244   $124.32   $124.30   $124.30  
  Purchase #7 $141.55   5.262%   $148.9984   $149.00   $149.00   $149.00  
  7 purchase totals = $1,142.94       $1,241.2935   $1,241.30   $1,241.35   $1,241.20