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 $87.44   10.226%   $96.3816   $96.38   $96.40   $96.40  
  Purchase #2 $218.28   12.218%   $244.9495   $244.95   $244.95   $244.90  
  Purchase #3 $172.75   4.848%   $181.1249   $181.12   $181.10   $181.10  
  Purchase #4 $193.49   5.168%   $203.4896   $203.49   $203.50   $203.50  
  Purchase #5 $89.85   4.473%   $93.869   $93.87   $93.85   $93.90  
  Purchase #6 $235.51   12.618%   $265.2267   $265.23   $265.25   $265.20  
  Purchase #7 $130.66   13.383%   $148.1462   $148.15   $148.15   $148.10  
  7 purchase totals = $1,127.98       $1,233.1875   $1,233.19   $1,233.20   $1,233.10