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 $48.51   8.555%   $52.66   $52.66   $52.65   $52.70  
  Purchase #2 $93.74   12.508%   $105.465   $105.47   $105.45   $105.50  
  Purchase #3 $183.92   8.517%   $199.5845   $199.58   $199.60   $199.60  
  Purchase #4 $233.82   4.283%   $243.8345   $243.83   $243.85   $243.80  
  Purchase #5 $5.75   6.266%   $6.1103   $6.11   $6.10   $6.10  
  Purchase #6 $159.34   7.158%   $170.7456   $170.75   $170.75   $170.70  
  Purchase #7 $215.66   9.320%   $235.7595   $235.76   $235.75   $235.80  
  7 purchase totals = $940.74       $1,014.1594   $1,014.16   $1,014.15   $1,014.20