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 $69.26   9.192%   $75.6264   $75.63   $75.65   $75.60  
  Purchase #2 $182.82   13.869%   $208.1753   $208.18   $208.20   $208.20  
  Purchase #3 $26.88   9.831%   $29.5226   $29.52   $29.50   $29.50  
  Purchase #4 $241.78   13.208%   $273.7143   $273.71   $273.70   $273.70  
  Purchase #5 $185.57   4.588%   $194.084   $194.08   $194.10   $194.10  
  Purchase #6 $12.75   8.800%   $13.872   $13.87   $13.85   $13.90  
  Purchase #7 $166.41   3.392%   $172.0546   $172.05   $172.05   $172.10  
  7 purchase totals = $885.47       $967.0492   $967.04   $967.05   $967.10