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 $245.45   7.773%   $264.5288   $264.53   $264.55   $264.50  
  Purchase #2 $26.59   9.836%   $29.2054   $29.21   $29.20   $29.20  
  Purchase #3 $218.65   12.741%   $246.5082   $246.51   $246.50   $246.50  
  Purchase #4 $80.33   8.735%   $87.3468   $87.35   $87.35   $87.30  
  Purchase #5 $120.87   10.359%   $133.3909   $133.39   $133.40   $133.40  
  Purchase #6 $25.48   8.128%   $27.551   $27.55   $27.55   $27.60  
  Purchase #7 $202.25   11.581%   $225.6726   $225.67   $225.65   $225.70  
  7 purchase totals = $919.62       $1,014.2037   $1,014.21   $1,014.20   $1,014.20