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 $67.82   11.457%   $75.5901   $75.59   $75.60   $75.60  
  Purchase #2 $106.89   8.113%   $115.562   $115.56   $115.55   $115.60  
  Purchase #3 $77.67   8.190%   $84.0312   $84.03   $84.05   $84.00  
  Purchase #4 $155.29   13.359%   $176.0352   $176.04   $176.05   $176.00  
  Purchase #5 $198.46   12.342%   $222.9539   $222.95   $222.95   $223.00  
  Purchase #6 $116.80   10.193%   $128.7054   $128.71   $128.70   $128.70  
  Purchase #7 $240.73   10.479%   $265.9561   $265.96   $265.95   $266.00  
  7 purchase totals = $963.66       $1,068.8339   $1,068.84   $1,068.85   $1,068.90