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 $212.53   8.672%   $230.9606   $230.96   $230.95   $231.00  
  Purchase #2 $216.28   7.110%   $231.6575   $231.66   $231.65   $231.70  
  Purchase #3 $92.26   10.813%   $102.2361   $102.24   $102.25   $102.20  
  Purchase #4 $75.76   10.367%   $83.614   $83.61   $83.60   $83.60  
  Purchase #5 $239.75   10.752%   $265.5279   $265.53   $265.55   $265.50  
  Purchase #6 $154.48   4.473%   $161.3899   $161.39   $161.40   $161.40  
  Purchase #7 $25.72   11.414%   $28.6557   $28.66   $28.65   $28.70  
  7 purchase totals = $1,016.78       $1,104.0417   $1,104.05   $1,104.05   $1,104.10