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 $39.38   10.694%   $43.5913   $43.59   $43.60   $43.60  
  Purchase #2 $114.67   9.850%   $125.965   $125.97   $125.95   $126.00  
  Purchase #3 $230.77   5.712%   $243.9516   $243.95   $243.95   $244.00  
  Purchase #4 $237.56   11.452%   $264.7654   $264.77   $264.75   $264.80  
  Purchase #5 $219.66   4.389%   $229.3009   $229.30   $229.30   $229.30  
  Purchase #6 $167.52   12.727%   $188.8403   $188.84   $188.85   $188.80  
  Purchase #7 $11.46   9.191%   $12.5133   $12.51   $12.50   $12.50  
  7 purchase totals = $1,021.02       $1,108.9278   $1,108.93   $1,108.90   $1,109.00