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 $162.31   5.323%   $170.9498   $170.95   $170.95   $170.90  
  Purchase #2 $120.53   3.678%   $124.9631   $124.96   $124.95   $125.00  
  Purchase #3 $216.75   9.616%   $237.5927   $237.59   $237.60   $237.60  
  Purchase #4 $203.85   3.417%   $210.8156   $210.82   $210.80   $210.80  
  Purchase #5 $202.56   10.547%   $223.924   $223.92   $223.90   $223.90  
  Purchase #6 $116.88   5.174%   $122.9274   $122.93   $122.95   $122.90  
  Purchase #7 $142.61   6.526%   $151.9167   $151.92   $151.90   $151.90  
  7 purchase totals = $1,165.49       $1,243.0893   $1,243.09   $1,243.05   $1,243.00