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 $92.81   4.312%   $96.812   $96.81   $96.80   $96.80  
  Purchase #2 $212.56   5.349%   $223.9298   $223.93   $223.95   $223.90  
  Purchase #3 $40.97   6.200%   $43.5101   $43.51   $43.50   $43.50  
  Purchase #4 $191.99   8.181%   $207.6967   $207.70   $207.70   $207.70  
  Purchase #5 $136.95   9.796%   $150.3656   $150.37   $150.35   $150.40  
  Purchase #6 $130.40   6.285%   $138.5956   $138.60   $138.60   $138.60  
  Purchase #7 $144.26   5.383%   $152.0255   $152.03   $152.05   $152.00  
  7 purchase totals = $949.94       $1,012.9353   $1,012.95   $1,012.95   $1,012.90