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 $130.37   8.665%   $141.6666   $141.67   $141.65   $141.70  
  Purchase #2 $193.56   7.147%   $207.3937   $207.39   $207.40   $207.40  
  Purchase #3 $86.27   11.176%   $95.9115   $95.91   $95.90   $95.90  
  Purchase #4 $21.77   4.668%   $22.7862   $22.79   $22.80   $22.80  
  Purchase #5 $22.47   8.152%   $24.3018   $24.30   $24.30   $24.30  
  Purchase #6 $84.25   6.609%   $89.8181   $89.82   $89.80   $89.80  
  Purchase #7 $192.26   7.137%   $205.9816   $205.98   $206.00   $206.00  
  7 purchase totals = $730.95       $787.8595   $787.86   $787.85   $787.90