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 $64.37   7.516%   $69.208   $69.21   $69.20   $69.20  
  Purchase #2 $211.83   3.267%   $218.7505   $218.75   $218.75   $218.80  
  Purchase #3 $201.85   4.560%   $211.0544   $211.05   $211.05   $211.10  
  Purchase #4 $160.79   8.202%   $173.978   $173.98   $174.00   $174.00  
  Purchase #5 $57.76   4.261%   $60.2212   $60.22   $60.20   $60.20  
  Purchase #6 $5.41   13.622%   $6.147   $6.15   $6.15   $6.10  
  Purchase #7 $46.30   4.464%   $48.3668   $48.37   $48.35   $48.40  
  7 purchase totals = $748.31       $787.7259   $787.73   $787.70   $787.80