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 $86.27   10.140%   $95.0178   $95.02   $95.00   $95.00  
  Purchase #2 $218.57   9.127%   $238.5189   $238.52   $238.50   $238.50  
  Purchase #3 $176.25   6.355%   $187.4507   $187.45   $187.45   $187.50  
  Purchase #4 $157.58   8.391%   $170.8025   $170.80   $170.80   $170.80  
  Purchase #5 $201.88   7.389%   $216.7969   $216.80   $216.80   $216.80  
  Purchase #6 $198.61   9.175%   $216.8325   $216.83   $216.85   $216.80  
  Purchase #7 $123.93   13.697%   $140.9047   $140.90   $140.90   $140.90  
  7 purchase totals = $1,163.09       $1,266.3240   $1,266.32   $1,266.30   $1,266.30