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 $100.51   13.566%   $114.1452   $114.15   $114.15   $114.10  
  Purchase #2 $232.85   7.779%   $250.9634   $250.96   $250.95   $251.00  
  Purchase #3 $26.74   8.592%   $29.0375   $29.04   $29.05   $29.00  
  Purchase #4 $184.97   5.177%   $194.5459   $194.55   $194.55   $194.50  
  Purchase #5 $43.77   11.629%   $48.86   $48.86   $48.85   $48.90  
  Purchase #6 $215.35   13.592%   $244.6204   $244.62   $244.60   $244.60  
  Purchase #7 $165.29   5.348%   $174.1297   $174.13   $174.15   $174.10  
  7 purchase totals = $969.48       $1,056.3021   $1,056.31   $1,056.30   $1,056.20