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 $114.56   11.623%   $127.8753   $127.88   $127.90   $127.90  
  Purchase #2 $42.76   5.281%   $45.0182   $45.02   $45.00   $45.00  
  Purchase #3 $250.69   8.195%   $271.234   $271.23   $271.25   $271.20  
  Purchase #4 $204.93   12.480%   $230.5053   $230.51   $230.50   $230.50  
  Purchase #5 $61.44   7.407%   $65.9909   $65.99   $66.00   $66.00  
  Purchase #6 $201.46   12.128%   $225.8931   $225.89   $225.90   $225.90  
  Purchase #7 $247.42   8.776%   $269.1336   $269.13   $269.15   $269.10  
  7 purchase totals = $1,123.26       $1,235.6504   $1,235.65   $1,235.70   $1,235.60