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 $183.52   6.390%   $195.2469   $195.25   $195.25   $195.20  
  Purchase #2 $246.72   4.844%   $258.6711   $258.67   $258.65   $258.70  
  Purchase #3 $48.85   9.225%   $53.3564   $53.36   $53.35   $53.40  
  Purchase #4 $194.88   8.370%   $211.1915   $211.19   $211.20   $211.20  
  Purchase #5 $98.36   7.202%   $105.4439   $105.44   $105.45   $105.40  
  Purchase #6 $143.63   8.713%   $156.1445   $156.14   $156.15   $156.10  
  Purchase #7 $53.31   6.657%   $56.8588   $56.86   $56.85   $56.90  
  7 purchase totals = $969.27       $1,036.9131   $1,036.91   $1,036.90   $1,036.90