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 $84.75   9.653%   $92.9309   $92.93   $92.95   $92.90  
  Purchase #2 $195.33   10.843%   $216.5096   $216.51   $216.50   $216.50  
  Purchase #3 $186.88   8.397%   $202.5723   $202.57   $202.55   $202.60  
  Purchase #4 $121.35   9.769%   $133.2047   $133.20   $133.20   $133.20  
  Purchase #5 $162.85   12.835%   $183.7518   $183.75   $183.75   $183.80  
  Purchase #6 $150.67   10.498%   $166.4873   $166.49   $166.50   $166.50  
  Purchase #7 $194.69   4.133%   $202.7365   $202.74   $202.75   $202.70  
  7 purchase totals = $1,096.52       $1,198.1931   $1,198.19   $1,198.20   $1,198.20