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 $86.29   10.576%   $95.416   $95.42   $95.40   $95.40  
  Purchase #2 $117.48   7.502%   $126.2933   $126.29   $126.30   $126.30  
  Purchase #3 $57.88   13.486%   $65.6857   $65.69   $65.70   $65.70  
  Purchase #4 $101.82   4.142%   $106.0374   $106.04   $106.05   $106.00  
  Purchase #5 $6.61   13.724%   $7.5172   $7.52   $7.50   $7.50  
  Purchase #6 $218.71   8.334%   $236.9373   $236.94   $236.95   $236.90  
  Purchase #7 $89.65   9.172%   $97.8727   $97.87   $97.85   $97.90  
  7 purchase totals = $678.44       $735.7596   $735.77   $735.75   $735.70