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 $89.77   5.444%   $94.6571   $94.66   $94.65   $94.70  
  Purchase #2 $102.37   12.302%   $114.9636   $114.96   $114.95   $115.00  
  Purchase #3 $235.30   5.566%   $248.3968   $248.40   $248.40   $248.40  
  Purchase #4 $34.60   8.824%   $37.6531   $37.65   $37.65   $37.70  
  Purchase #5 $191.37   4.331%   $199.6582   $199.66   $199.65   $199.70  
  Purchase #6 $206.70   12.198%   $231.9133   $231.91   $231.90   $231.90  
  Purchase #7 $117.97   7.242%   $126.5134   $126.51   $126.50   $126.50  
  7 purchase totals = $978.08       $1,053.7555   $1,053.75   $1,053.70   $1,053.90