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 $88.36   7.799%   $95.2512   $95.25   $95.25   $95.30  
  Purchase #2 $193.30   9.693%   $212.0366   $212.04   $212.05   $212.00  
  Purchase #3 $210.61   11.289%   $234.3858   $234.39   $234.40   $234.40  
  Purchase #4 $143.90   13.639%   $163.5265   $163.53   $163.55   $163.50  
  Purchase #5 $11.97   3.191%   $12.352   $12.35   $12.35   $12.40  
  Purchase #6 $234.86   12.258%   $263.6491   $263.65   $263.65   $263.60  
  Purchase #7 $160.30   12.103%   $179.7011   $179.70   $179.70   $179.70  
  7 purchase totals = $1,043.30       $1,160.9023   $1,160.91   $1,160.95   $1,160.90