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 $193.31   4.561%   $202.1269   $202.13   $202.15   $202.10  
  Purchase #2 $46.37   13.562%   $52.6587   $52.66   $52.65   $52.70  
  Purchase #3 $232.46   11.671%   $259.5904   $259.59   $259.60   $259.60  
  Purchase #4 $18.90   7.853%   $20.3842   $20.38   $20.40   $20.40  
  Purchase #5 $123.49   9.700%   $135.4685   $135.47   $135.45   $135.50  
  Purchase #6 $149.96   8.226%   $162.2957   $162.30   $162.30   $162.30  
  Purchase #7 $249.76   5.141%   $262.6002   $262.60   $262.60   $262.60  
  7 purchase totals = $1,014.25       $1,095.1246   $1,095.13   $1,095.15   $1,095.20