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 $182.92   9.426%   $200.162   $200.16   $200.15   $200.20  
  Purchase #2 $165.81   7.269%   $177.8627   $177.86   $177.85   $177.90  
  Purchase #3 $230.73   4.784%   $241.7681   $241.77   $241.75   $241.80  
  Purchase #4 $168.67   3.697%   $174.9057   $174.91   $174.90   $174.90  
  Purchase #5 $176.84   11.512%   $197.1978   $197.20   $197.20   $197.20  
  Purchase #6 $11.53   4.179%   $12.0118   $12.01   $12.00   $12.00  
  Purchase #7 $7.37   8.417%   $7.9903   $7.99   $8.00   $8.00  
  7 purchase totals = $943.87       $1,011.8984   $1,011.90   $1,011.85   $1,012.00