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 $127.81   7.695%   $137.645   $137.65   $137.65   $137.60  
  Purchase #2 $225.45   13.339%   $255.5228   $255.52   $255.50   $255.50  
  Purchase #3 $125.42   3.387%   $129.668   $129.67   $129.65   $129.70  
  Purchase #4 $128.25   10.555%   $141.7868   $141.79   $141.80   $141.80  
  Purchase #5 $65.99   7.507%   $70.9439   $70.94   $70.95   $70.90  
  Purchase #6 $95.38   13.523%   $108.2782   $108.28   $108.30   $108.30  
  Purchase #7 $155.97   9.416%   $170.6561   $170.66   $170.65   $170.70  
  7 purchase totals = $924.27       $1,014.5008   $1,014.51   $1,014.50   $1,014.50