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 $92.54   3.201%   $95.5022   $95.50   $95.50   $95.50  
  Purchase #2 $8.45   8.496%   $9.1679   $9.17   $9.15   $9.20  
  Purchase #3 $57.92   13.122%   $65.5203   $65.52   $65.50   $65.50  
  Purchase #4 $150.76   5.666%   $159.3021   $159.30   $159.30   $159.30  
  Purchase #5 $209.61   11.831%   $234.409   $234.41   $234.40   $234.40  
  Purchase #6 $239.37   3.628%   $248.0543   $248.05   $248.05   $248.10  
  Purchase #7 $216.60   6.639%   $230.9801   $230.98   $231.00   $231.00  
  7 purchase totals = $975.25       $1,042.9359   $1,042.93   $1,042.90   $1,043.00