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 $59.45   5.159%   $62.517   $62.52   $62.50   $62.50  
  Purchase #2 $89.52   10.740%   $99.1344   $99.13   $99.15   $99.10  
  Purchase #3 $95.81   6.147%   $101.6994   $101.70   $101.70   $101.70  
  Purchase #4 $45.70   7.423%   $49.0923   $49.09   $49.10   $49.10  
  Purchase #5 $237.36   9.362%   $259.5816   $259.58   $259.60   $259.60  
  Purchase #6 $134.98   12.243%   $151.5056   $151.51   $151.50   $151.50  
  Purchase #7 $189.68   6.572%   $202.1458   $202.15   $202.15   $202.10  
  7 purchase totals = $852.50       $925.6761   $925.68   $925.70   $925.60