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 $95.75   5.435%   $100.954   $100.95   $100.95   $101.00  
  Purchase #2 $121.91   6.356%   $129.6586   $129.66   $129.65   $129.70  
  Purchase #3 $124.60   8.821%   $135.591   $135.59   $135.60   $135.60  
  Purchase #4 $178.97   12.665%   $201.6366   $201.64   $201.65   $201.60  
  Purchase #5 $135.90   4.803%   $142.4273   $142.43   $142.45   $142.40  
  Purchase #6 $33.99   4.410%   $35.489   $35.49   $35.50   $35.50  
  Purchase #7 $194.47   5.450%   $205.0686   $205.07   $205.05   $205.10  
  7 purchase totals = $885.59       $950.8251   $950.83   $950.85   $950.90