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 $95.49   8.184%   $103.3049   $103.30   $103.30   $103.30  
  Purchase #2 $44.88   8.217%   $48.5678   $48.57   $48.55   $48.60  
  Purchase #3 $52.51   11.648%   $58.6264   $58.63   $58.65   $58.60  
  Purchase #4 $246.82   5.306%   $259.9163   $259.92   $259.90   $259.90  
  Purchase #5 $219.47   12.625%   $247.1781   $247.18   $247.20   $247.20  
  Purchase #6 $201.27   5.302%   $211.9413   $211.94   $211.95   $211.90  
  Purchase #7 $146.52   6.728%   $156.3779   $156.38   $156.40   $156.40  
  7 purchase totals = $1,006.96       $1,085.9127   $1,085.92   $1,085.95   $1,085.90