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 $59.45   9.507%   $65.1019   $65.10   $65.10   $65.10  
  Purchase #2 $166.74   11.363%   $185.6867   $185.69   $185.70   $185.70  
  Purchase #3 $195.32   7.287%   $209.553   $209.55   $209.55   $209.60  
  Purchase #4 $237.31   6.508%   $252.7541   $252.75   $252.75   $252.80  
  Purchase #5 $194.86   8.798%   $212.0038   $212.00   $212.00   $212.00  
  Purchase #6 $228.45   6.327%   $242.904   $242.90   $242.90   $242.90  
  Purchase #7 $144.82   11.259%   $161.1253   $161.13   $161.15   $161.10  
  7 purchase totals = $1,226.95       $1,329.1288   $1,329.12   $1,329.15   $1,329.20