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 $210.31   10.792%   $233.0067   $233.01   $233.00   $233.00  
  Purchase #2 $27.56   11.589%   $30.7539   $30.75   $30.75   $30.80  
  Purchase #3 $87.33   6.276%   $92.8108   $92.81   $92.80   $92.80  
  Purchase #4 $176.42   5.568%   $186.2431   $186.24   $186.25   $186.20  
  Purchase #5 $120.48   5.160%   $126.6968   $126.70   $126.70   $126.70  
  Purchase #6 $228.84   9.860%   $251.4036   $251.40   $251.40   $251.40  
  Purchase #7 $223.44   13.385%   $253.3474   $253.35   $253.35   $253.30  
  7 purchase totals = $1,074.38       $1,174.2623   $1,174.26   $1,174.25   $1,174.20