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 $197.57   8.418%   $214.2014   $214.20   $214.20   $214.20  
  Purchase #2 $89.37   13.316%   $101.2705   $101.27   $101.25   $101.30  
  Purchase #3 $237.83   4.277%   $248.002   $248.00   $248.00   $248.00  
  Purchase #4 $146.30   3.141%   $150.8953   $150.90   $150.90   $150.90  
  Purchase #5 $136.84   7.578%   $147.2097   $147.21   $147.20   $147.20  
  Purchase #6 $169.29   13.292%   $191.792   $191.79   $191.80   $191.80  
  Purchase #7 $56.95   8.268%   $61.6586   $61.66   $61.65   $61.70  
  7 purchase totals = $1,034.15       $1,115.0295   $1,115.03   $1,115.00   $1,115.10