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 $41.49   4.382%   $43.3081   $43.31   $43.30   $43.30  
  Purchase #2 $187.61   12.238%   $210.5697   $210.57   $210.55   $210.60  
  Purchase #3 $102.91   4.190%   $107.2219   $107.22   $107.20   $107.20  
  Purchase #4 $156.66   13.407%   $177.6634   $177.66   $177.65   $177.70  
  Purchase #5 $141.78   13.836%   $161.3967   $161.40   $161.40   $161.40  
  Purchase #6 $243.80   9.485%   $266.9244   $266.92   $266.90   $266.90  
  Purchase #7 $45.50   3.263%   $46.9847   $46.98   $47.00   $47.00  
  7 purchase totals = $919.75       $1,014.0689   $1,014.06   $1,014.00   $1,014.10