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 $176.97   10.457%   $195.4758   $195.48   $195.50   $195.50  
  Purchase #2 $86.88   7.394%   $93.3039   $93.30   $93.30   $93.30  
  Purchase #3 $211.27   9.307%   $230.9329   $230.93   $230.95   $230.90  
  Purchase #4 $122.95   5.637%   $129.8807   $129.88   $129.90   $129.90  
  Purchase #5 $48.72   11.395%   $54.2716   $54.27   $54.25   $54.30  
  Purchase #6 $208.85   7.816%   $225.1737   $225.17   $225.15   $225.20  
  Purchase #7 $165.82   7.547%   $178.3344   $178.33   $178.35   $178.30  
  7 purchase totals = $1,021.46       $1,107.3730   $1,107.36   $1,107.40   $1,107.40