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 $86.36   6.510%   $91.982   $91.98   $92.00   $92.00  
  Purchase #2 $90.97   12.765%   $102.5823   $102.58   $102.60   $102.60  
  Purchase #3 $156.73   5.849%   $165.8971   $165.90   $165.90   $165.90  
  Purchase #4 $226.62   13.536%   $257.2953   $257.30   $257.30   $257.30  
  Purchase #5 $219.78   5.575%   $232.0327   $232.03   $232.05   $232.00  
  Purchase #6 $140.52   3.837%   $145.9118   $145.91   $145.90   $145.90  
  Purchase #7 $101.77   12.275%   $114.2623   $114.26   $114.25   $114.30  
  7 purchase totals = $1,022.75       $1,109.9635   $1,109.96   $1,110.00   $1,110.00