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 $181.50   8.243%   $196.461   $196.46   $196.45   $196.50  
  Purchase #2 $140.79   6.232%   $149.564   $149.56   $149.55   $149.60  
  Purchase #3 $23.69   5.112%   $24.901   $24.90   $24.90   $24.90  
  Purchase #4 $164.84   11.632%   $184.0142   $184.01   $184.00   $184.00  
  Purchase #5 $167.74   5.135%   $176.3534   $176.35   $176.35   $176.40  
  Purchase #6 $141.31   7.550%   $151.9789   $151.98   $152.00   $152.00  
  Purchase #7 $8.45   7.185%   $9.0571   $9.06   $9.05   $9.10  
  7 purchase totals = $828.32       $892.3296   $892.32   $892.30   $892.50