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 $167.29   7.553%   $179.9254   $179.93   $179.95   $179.90  
  Purchase #2 $69.81   6.169%   $74.1166   $74.12   $74.10   $74.10  
  Purchase #3 $117.74   11.447%   $131.2177   $131.22   $131.20   $131.20  
  Purchase #4 $216.48   7.425%   $232.5536   $232.55   $232.55   $232.60  
  Purchase #5 $34.34   5.214%   $36.1305   $36.13   $36.15   $36.10  
  Purchase #6 $196.53   8.460%   $213.1564   $213.16   $213.15   $213.20  
  Purchase #7 $212.35   6.729%   $226.639   $226.64   $226.65   $226.60  
  7 purchase totals = $1,014.54       $1,093.7392   $1,093.75   $1,093.75   $1,093.70