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 $231.83   4.365%   $241.9494   $241.95   $241.95   $241.90  
  Purchase #2 $64.54   7.166%   $69.1649   $69.16   $69.15   $69.20  
  Purchase #3 $80.27   3.731%   $83.2649   $83.26   $83.25   $83.30  
  Purchase #4 $239.84   11.864%   $268.2946   $268.29   $268.30   $268.30  
  Purchase #5 $91.64   6.749%   $97.8248   $97.82   $97.80   $97.80  
  Purchase #6 $98.86   3.474%   $102.2944   $102.29   $102.30   $102.30  
  Purchase #7 $207.81   12.477%   $233.7385   $233.74   $233.75   $233.70  
  7 purchase totals = $1,014.79       $1,096.5315   $1,096.51   $1,096.50   $1,096.50