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 $165.74   5.613%   $175.043   $175.04   $175.05   $175.00  
  Purchase #2 $161.43   10.223%   $177.933   $177.93   $177.95   $177.90  
  Purchase #3 $202.63   5.839%   $214.4616   $214.46   $214.45   $214.50  
  Purchase #4 $166.59   6.595%   $177.5766   $177.58   $177.60   $177.60  
  Purchase #5 $247.98   12.694%   $279.4586   $279.46   $279.45   $279.50  
  Purchase #6 $101.52   5.330%   $106.931   $106.93   $106.95   $106.90  
  Purchase #7 $113.47   6.861%   $121.2552   $121.26   $121.25   $121.30  
  7 purchase totals = $1,159.36       $1,252.6590   $1,252.66   $1,252.70   $1,252.70