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 $204.77   3.818%   $212.5881   $212.59   $212.60   $212.60  
  Purchase #2 $211.51   11.272%   $235.3514   $235.35   $235.35   $235.40  
  Purchase #3 $110.91   7.783%   $119.5421   $119.54   $119.55   $119.50  
  Purchase #4 $127.97   13.582%   $145.3509   $145.35   $145.35   $145.40  
  Purchase #5 $195.49   6.292%   $207.7902   $207.79   $207.80   $207.80  
  Purchase #6 $211.91   7.103%   $226.962   $226.96   $226.95   $227.00  
  Purchase #7 $50.95   11.815%   $56.9697   $56.97   $56.95   $57.00  
  7 purchase totals = $1,113.51       $1,204.5544   $1,204.55   $1,204.55   $1,204.70