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 $227.29   6.134%   $241.232   $241.23   $241.25   $241.20  
  Purchase #2 $95.70   11.248%   $106.4643   $106.46   $106.45   $106.50  
  Purchase #3 $200.67   5.780%   $212.2687   $212.27   $212.25   $212.30  
  Purchase #4 $32.51   9.455%   $35.5838   $35.58   $35.60   $35.60  
  Purchase #5 $223.75   9.359%   $244.6908   $244.69   $244.70   $244.70  
  Purchase #6 $19.28   6.356%   $20.5054   $20.51   $20.50   $20.50  
  Purchase #7 $174.65   11.613%   $194.9321   $194.93   $194.95   $194.90  
  7 purchase totals = $973.85       $1,055.6771   $1,055.67   $1,055.70   $1,055.70