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 $163.52   8.230%   $176.9777   $176.98   $177.00   $177.00  
  Purchase #2 $26.90   10.213%   $29.6473   $29.65   $29.65   $29.60  
  Purchase #3 $227.48   3.844%   $236.2243   $236.22   $236.20   $236.20  
  Purchase #4 $196.39   7.679%   $211.4708   $211.47   $211.45   $211.50  
  Purchase #5 $180.50   11.657%   $201.5409   $201.54   $201.55   $201.50  
  Purchase #6 $186.32   11.120%   $207.0388   $207.04   $207.05   $207.00  
  Purchase #7 $29.62   8.165%   $32.0385   $32.04   $32.05   $32.00  
  7 purchase totals = $1,010.73       $1,094.9383   $1,094.94   $1,094.95   $1,094.80