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 $216.81   7.571%   $233.2247   $233.22   $233.20   $233.20  
  Purchase #2 $25.35   13.783%   $28.844   $28.84   $28.85   $28.80  
  Purchase #3 $201.80   8.135%   $218.2164   $218.22   $218.20   $218.20  
  Purchase #4 $192.27   5.140%   $202.1527   $202.15   $202.15   $202.20  
  Purchase #5 $87.81   6.175%   $93.2323   $93.23   $93.25   $93.20  
  Purchase #6 $162.49   7.219%   $174.2202   $174.22   $174.20   $174.20  
  Purchase #7 $105.34   4.471%   $110.0498   $110.05   $110.05   $110.00  
  7 purchase totals = $991.87       $1,059.9401   $1,059.93   $1,059.90   $1,059.80