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 $64.38   4.162%   $67.0595   $67.06   $67.05   $67.10  
  Purchase #2 $205.41   3.829%   $213.2751   $213.28   $213.30   $213.30  
  Purchase #3 $243.43   9.607%   $266.8163   $266.82   $266.80   $266.80  
  Purchase #4 $134.82   9.410%   $147.5066   $147.51   $147.50   $147.50  
  Purchase #5 $65.84   6.868%   $70.3619   $70.36   $70.35   $70.40  
  Purchase #6 $82.49   12.831%   $93.0743   $93.07   $93.05   $93.10  
  Purchase #7 $161.40   8.133%   $174.5267   $174.53   $174.55   $174.50  
  7 purchase totals = $957.77       $1,032.6204   $1,032.63   $1,032.60   $1,032.70