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 $192.92   6.575%   $205.6045   $205.60   $205.60   $205.60  
  Purchase #2 $101.28   9.196%   $110.5937   $110.59   $110.60   $110.60  
  Purchase #3 $72.80   5.109%   $76.5194   $76.52   $76.50   $76.50  
  Purchase #4 $172.56   10.577%   $190.8117   $190.81   $190.80   $190.80  
  Purchase #5 $131.54   13.846%   $149.753   $149.75   $149.75   $149.80  
  Purchase #6 $245.38   13.171%   $277.699   $277.70   $277.70   $277.70  
  Purchase #7 $233.38   10.380%   $257.6048   $257.60   $257.60   $257.60  
  7 purchase totals = $1,149.86       $1,268.5861   $1,268.57   $1,268.55   $1,268.60