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 $69.41   6.167%   $73.6905   $73.69   $73.70   $73.70  
  Purchase #2 $26.57   13.852%   $30.2505   $30.25   $30.25   $30.30  
  Purchase #3 $170.89   11.560%   $190.6449   $190.64   $190.65   $190.60  
  Purchase #4 $206.73   8.349%   $223.9899   $223.99   $224.00   $224.00  
  Purchase #5 $194.25   3.461%   $200.973   $200.97   $200.95   $201.00  
  Purchase #6 $108.43   13.571%   $123.145   $123.15   $123.15   $123.10  
  Purchase #7 $198.27   3.194%   $204.6027   $204.60   $204.60   $204.60  
  7 purchase totals = $974.55       $1,047.2965   $1,047.29   $1,047.30   $1,047.30