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 $71.47   6.268%   $75.9497   $75.95   $75.95   $75.90  
  Purchase #2 $176.54   4.414%   $184.3325   $184.33   $184.35   $184.30  
  Purchase #3 $213.80   4.436%   $223.2842   $223.28   $223.30   $223.30  
  Purchase #4 $198.95   6.444%   $211.7703   $211.77   $211.75   $211.80  
  Purchase #5 $65.96   11.353%   $73.4484   $73.45   $73.45   $73.40  
  Purchase #6 $138.63   4.322%   $144.6216   $144.62   $144.60   $144.60  
  Purchase #7 $33.37   6.315%   $35.4773   $35.48   $35.50   $35.50  
  7 purchase totals = $898.72       $948.8840   $948.88   $948.90   $948.80