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 $61.97   5.805%   $65.5674   $65.57   $65.55   $65.60  
  Purchase #2 $133.48   11.262%   $148.5125   $148.51   $148.50   $148.50  
  Purchase #3 $143.92   6.673%   $153.5238   $153.52   $153.50   $153.50  
  Purchase #4 $195.66   6.872%   $209.1058   $209.11   $209.10   $209.10  
  Purchase #5 $67.37   11.442%   $75.0785   $75.08   $75.10   $75.10  
  Purchase #6 $167.95   3.737%   $174.2263   $174.23   $174.25   $174.20  
  Purchase #7 $224.92   9.834%   $247.0386   $247.04   $247.05   $247.00  
  7 purchase totals = $995.27       $1,073.0529   $1,073.06   $1,073.05   $1,073.00