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 $198.59   4.260%   $207.0499   $207.05   $207.05   $207.00  
  Purchase #2 $46.71   9.342%   $51.0736   $51.07   $51.05   $51.10  
  Purchase #3 $38.56   10.485%   $42.603   $42.60   $42.60   $42.60  
  Purchase #4 $204.42   6.313%   $217.325   $217.33   $217.35   $217.30  
  Purchase #5 $230.65   4.288%   $240.5403   $240.54   $240.55   $240.50  
  Purchase #6 $76.42   3.522%   $79.1115   $79.11   $79.10   $79.10  
  Purchase #7 $200.85   7.596%   $216.1066   $216.11   $216.10   $216.10  
  7 purchase totals = $996.20       $1,053.8099   $1,053.81   $1,053.80   $1,053.70