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 $84.68   13.325%   $95.9636   $95.96   $95.95   $96.00  
  Purchase #2 $211.58   12.199%   $237.3906   $237.39   $237.40   $237.40  
  Purchase #3 $63.35   7.329%   $67.9929   $67.99   $68.00   $68.00  
  Purchase #4 $152.52   10.457%   $168.469   $168.47   $168.45   $168.50  
  Purchase #5 $61.43   9.807%   $67.4544   $67.45   $67.45   $67.50  
  Purchase #6 $197.60   3.554%   $204.6227   $204.62   $204.60   $204.60  
  Purchase #7 $23.91   13.236%   $27.0747   $27.07   $27.05   $27.10  
  7 purchase totals = $795.07       $868.9679   $868.95   $868.90   $869.10