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 $148.40   11.217%   $165.046   $165.05   $165.05   $165.00  
  Purchase #2 $162.61   13.198%   $184.0713   $184.07   $184.05   $184.10  
  Purchase #3 $57.57   7.632%   $61.9637   $61.96   $61.95   $62.00  
  Purchase #4 $208.48   12.191%   $233.8958   $233.90   $233.90   $233.90  
  Purchase #5 $16.72   13.564%   $18.9879   $18.99   $19.00   $19.00  
  Purchase #6 $212.75   12.222%   $238.7523   $238.75   $238.75   $238.80  
  Purchase #7 $206.27   8.234%   $223.2543   $223.25   $223.25   $223.30  
  7 purchase totals = $1,012.80       $1,125.9713   $1,125.97   $1,125.95   $1,126.10