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 $70.98   3.522%   $73.4799   $73.48   $73.50   $73.50  
  Purchase #2 $180.79   11.668%   $201.8846   $201.88   $201.90   $201.90  
  Purchase #3 $176.73   3.343%   $182.6381   $182.64   $182.65   $182.60  
  Purchase #4 $163.53   9.361%   $178.838   $178.84   $178.85   $178.80  
  Purchase #5 $184.86   9.583%   $202.5751   $202.58   $202.60   $202.60  
  Purchase #6 $177.46   11.386%   $197.6656   $197.67   $197.65   $197.70  
  Purchase #7 $55.52   7.238%   $59.5385   $59.54   $59.55   $59.50  
  7 purchase totals = $1,009.87       $1,096.6198   $1,096.63   $1,096.70   $1,096.60