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 $160.31   9.555%   $175.6276   $175.63   $175.65   $175.60  
  Purchase #2 $130.35   5.359%   $137.3355   $137.34   $137.35   $137.30  
  Purchase #3 $45.33   5.679%   $47.9043   $47.90   $47.90   $47.90  
  Purchase #4 $226.32   3.805%   $234.9315   $234.93   $234.95   $234.90  
  Purchase #5 $113.54   4.345%   $118.4733   $118.47   $118.45   $118.50  
  Purchase #6 $153.48   5.238%   $161.5193   $161.52   $161.50   $161.50  
  Purchase #7 $122.49   10.215%   $135.0024   $135.00   $135.00   $135.00  
  7 purchase totals = $951.82       $1,010.7939   $1,010.79   $1,010.80   $1,010.70