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 $155.35   5.270%   $163.5369   $163.54   $163.55   $163.50  
  Purchase #2 $120.96   4.556%   $126.4709   $126.47   $126.45   $126.50  
  Purchase #3 $249.85   4.259%   $260.4911   $260.49   $260.50   $260.50  
  Purchase #4 $68.90   3.540%   $71.3391   $71.34   $71.35   $71.30  
  Purchase #5 $181.99   6.652%   $194.096   $194.10   $194.10   $194.10  
  Purchase #6 $39.64   13.282%   $44.905   $44.91   $44.90   $44.90  
  Purchase #7 $244.66   7.254%   $262.4076   $262.41   $262.40   $262.40  
  7 purchase totals = $1,061.35       $1,123.2466   $1,123.26   $1,123.25   $1,123.20