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 $56.51   5.208%   $59.453   $59.45   $59.45   $59.50  
  Purchase #2 $107.79   9.407%   $117.9298   $117.93   $117.95   $117.90  
  Purchase #3 $97.39   5.136%   $102.392   $102.39   $102.40   $102.40  
  Purchase #4 $174.93   10.182%   $192.7414   $192.74   $192.75   $192.70  
  Purchase #5 $50.62   6.230%   $53.7736   $53.77   $53.75   $53.80  
  Purchase #6 $114.69   5.707%   $121.2354   $121.24   $121.25   $121.20  
  Purchase #7 $55.48   8.345%   $60.1098   $60.11   $60.10   $60.10  
  7 purchase totals = $657.41       $707.6350   $707.63   $707.65   $707.60