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 $56.88   10.336%   $62.7591   $62.76   $62.75   $62.80  
  Purchase #2 $136.52   3.714%   $141.5904   $141.59   $141.60   $141.60  
  Purchase #3 $168.35   8.722%   $183.0335   $183.03   $183.05   $183.00  
  Purchase #4 $55.76   6.332%   $59.2907   $59.29   $59.30   $59.30  
  Purchase #5 $35.52   8.617%   $38.5808   $38.58   $38.60   $38.60  
  Purchase #6 $97.47   8.872%   $106.1175   $106.12   $106.10   $106.10  
  Purchase #7 $248.74   5.755%   $263.055   $263.06   $263.05   $263.10  
  7 purchase totals = $799.24       $854.4270   $854.43   $854.45   $854.50