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 $63.30   8.361%   $68.5925   $68.59   $68.60   $68.60  
  Purchase #2 $208.82   10.334%   $230.3995   $230.40   $230.40   $230.40  
  Purchase #3 $34.73   4.781%   $36.3904   $36.39   $36.40   $36.40  
  Purchase #4 $123.57   9.356%   $135.1312   $135.13   $135.15   $135.10  
  Purchase #5 $111.50   6.231%   $118.4476   $118.45   $118.45   $118.40  
  Purchase #6 $53.38   10.364%   $58.9123   $58.91   $58.90   $58.90  
  Purchase #7 $69.69   6.417%   $74.162   $74.16   $74.15   $74.20  
  7 purchase totals = $664.99       $722.0355   $722.03   $722.05   $722.00