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 $184.94   9.137%   $201.838   $201.84   $201.85   $201.80  
  Purchase #2 $116.93   8.465%   $126.8281   $126.83   $126.85   $126.80  
  Purchase #3 $132.41   3.517%   $137.0669   $137.07   $137.05   $137.10  
  Purchase #4 $111.60   11.637%   $124.5869   $124.59   $124.60   $124.60  
  Purchase #5 $241.92   13.140%   $273.7083   $273.71   $273.70   $273.70  
  Purchase #6 $243.85   10.207%   $268.7398   $268.74   $268.75   $268.70  
  Purchase #7 $77.26   5.370%   $81.4089   $81.41   $81.40   $81.40  
  7 purchase totals = $1,108.91       $1,214.1769   $1,214.19   $1,214.20   $1,214.10