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 $151.61   10.495%   $167.5215   $167.52   $167.50   $167.50  
  Purchase #2 $194.63   4.202%   $202.8084   $202.81   $202.80   $202.80  
  Purchase #3 $181.76   11.403%   $202.4861   $202.49   $202.50   $202.50  
  Purchase #4 $119.32   4.539%   $124.7359   $124.74   $124.75   $124.70  
  Purchase #5 $143.47   11.327%   $159.7208   $159.72   $159.70   $159.70  
  Purchase #6 $102.81   7.414%   $110.4323   $110.43   $110.45   $110.40  
  Purchase #7 $52.50   10.134%   $57.8204   $57.82   $57.80   $57.80  
  7 purchase totals = $946.10       $1,025.5254   $1,025.53   $1,025.50   $1,025.40