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 $68.49   9.499%   $74.9959   $75.00   $75.00   $75.00  
  Purchase #2 $114.36   5.464%   $120.6086   $120.61   $120.60   $120.60  
  Purchase #3 $143.56   7.281%   $154.0126   $154.01   $154.00   $154.00  
  Purchase #4 $29.52   6.612%   $31.4719   $31.47   $31.45   $31.50  
  Purchase #5 $123.45   9.290%   $134.9185   $134.92   $134.90   $134.90  
  Purchase #6 $147.55   10.276%   $162.7122   $162.71   $162.70   $162.70  
  Purchase #7 $62.52   7.443%   $67.1734   $67.17   $67.15   $67.20  
  7 purchase totals = $689.45       $745.8931   $745.89   $745.80   $745.90