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 $109.56   6.183%   $116.3341   $116.33   $116.35   $116.30  
  Purchase #2 $86.43   6.849%   $92.3496   $92.35   $92.35   $92.30  
  Purchase #3 $219.33   9.187%   $239.4798   $239.48   $239.50   $239.50  
  Purchase #4 $203.47   4.126%   $211.8652   $211.87   $211.85   $211.90  
  Purchase #5 $242.34   12.439%   $272.4847   $272.48   $272.50   $272.50  
  Purchase #6 $201.89   3.118%   $208.1849   $208.18   $208.20   $208.20  
  Purchase #7 $61.36   10.629%   $67.882   $67.88   $67.90   $67.90  
  7 purchase totals = $1,124.38       $1,208.5803   $1,208.57   $1,208.65   $1,208.60