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 $61.93   9.178%   $67.6139   $67.61   $67.60   $67.60  
  Purchase #2 $244.65   3.156%   $252.3712   $252.37   $252.35   $252.40  
  Purchase #3 $32.76   9.761%   $35.9577   $35.96   $35.95   $36.00  
  Purchase #4 $160.78   8.180%   $173.9318   $173.93   $173.95   $173.90  
  Purchase #5 $246.66   12.662%   $277.8921   $277.89   $277.90   $277.90  
  Purchase #6 $38.53   4.239%   $40.1633   $40.16   $40.15   $40.20  
  Purchase #7 $156.48   6.726%   $167.0048   $167.00   $167.00   $167.00  
  7 purchase totals = $941.79       $1,014.9348   $1,014.92   $1,014.90   $1,015.00