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 $59.38   10.574%   $65.6588   $65.66   $65.65   $65.70  
  Purchase #2 $228.39   12.860%   $257.761   $257.76   $257.75   $257.80  
  Purchase #3 $11.53   6.238%   $12.2492   $12.25   $12.25   $12.20  
  Purchase #4 $153.80   8.701%   $167.1821   $167.18   $167.20   $167.20  
  Purchase #5 $86.62   7.152%   $92.8151   $92.82   $92.80   $92.80  
  Purchase #6 $228.43   10.843%   $253.1987   $253.20   $253.20   $253.20  
  Purchase #7 $246.26   8.497%   $267.1847   $267.18   $267.20   $267.20  
  7 purchase totals = $1,014.41       $1,116.0496   $1,116.05   $1,116.05   $1,116.10