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 $94.85   13.649%   $107.7961   $107.80   $107.80   $107.80  
  Purchase #2 $218.49   5.369%   $230.2207   $230.22   $230.20   $230.20  
  Purchase #3 $169.75   13.142%   $192.0585   $192.06   $192.05   $192.10  
  Purchase #4 $50.71   5.167%   $53.3302   $53.33   $53.35   $53.30  
  Purchase #5 $220.84   9.245%   $241.2567   $241.26   $241.25   $241.30  
  Purchase #6 $106.36   3.176%   $109.738   $109.74   $109.75   $109.70  
  Purchase #7 $249.67   4.537%   $260.9975   $261.00   $261.00   $261.00  
  7 purchase totals = $1,110.67       $1,195.3977   $1,195.41   $1,195.40   $1,195.40