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 $205.61   4.525%   $214.9139   $214.91   $214.90   $214.90  
  Purchase #2 $33.58   9.790%   $36.8675   $36.87   $36.85   $36.90  
  Purchase #3 $46.68   4.750%   $48.8973   $48.90   $48.90   $48.90  
  Purchase #4 $62.52   3.594%   $64.767   $64.77   $64.75   $64.80  
  Purchase #5 $239.37   10.220%   $263.8336   $263.83   $263.85   $263.80  
  Purchase #6 $67.56   10.472%   $74.6349   $74.63   $74.65   $74.60  
  Purchase #7 $57.28   5.558%   $60.4636   $60.46   $60.45   $60.50  
  7 purchase totals = $712.60       $764.3778   $764.37   $764.35   $764.40