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 $91.58   3.816%   $95.0747   $95.07   $95.05   $95.10  
  Purchase #2 $162.44   8.322%   $175.9583   $175.96   $175.95   $176.00  
  Purchase #3 $41.69   3.623%   $43.2004   $43.20   $43.20   $43.20  
  Purchase #4 $165.38   10.669%   $183.0244   $183.02   $183.00   $183.00  
  Purchase #5 $184.35   13.805%   $209.7995   $209.80   $209.80   $209.80  
  Purchase #6 $51.78   11.108%   $57.5317   $57.53   $57.55   $57.50  
  Purchase #7 $6.55   13.405%   $7.428   $7.43   $7.45   $7.40  
  7 purchase totals = $703.77       $772.0170   $772.01   $772.00   $772.00