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 $58.60   6.229%   $62.2502   $62.25   $62.25   $62.30  
  Purchase #2 $241.54   4.778%   $253.0808   $253.08   $253.10   $253.10  
  Purchase #3 $238.53   13.512%   $270.7602   $270.76   $270.75   $270.80  
  Purchase #4 $183.56   8.347%   $198.8818   $198.88   $198.90   $198.90  
  Purchase #5 $206.68   9.309%   $225.9198   $225.92   $225.90   $225.90  
  Purchase #6 $99.27   7.777%   $106.9902   $106.99   $107.00   $107.00  
  Purchase #7 $231.95   11.293%   $258.1441   $258.14   $258.15   $258.10  
  7 purchase totals = $1,260.13       $1,376.0271   $1,376.02   $1,376.05   $1,376.10