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 $65.83   5.489%   $69.4434   $69.44   $69.45   $69.40  
  Purchase #2 $162.27   3.485%   $167.9251   $167.93   $167.95   $167.90  
  Purchase #3 $229.59   4.134%   $239.0813   $239.08   $239.10   $239.10  
  Purchase #4 $41.83   10.874%   $46.3786   $46.38   $46.40   $46.40  
  Purchase #5 $243.57   5.843%   $257.8018   $257.80   $257.80   $257.80  
  Purchase #6 $195.66   5.290%   $206.0104   $206.01   $206.00   $206.00  
  Purchase #7 $103.79   5.160%   $109.1456   $109.15   $109.15   $109.10  
  7 purchase totals = $1,042.54       $1,095.7862   $1,095.79   $1,095.85   $1,095.70