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 $238.63   8.851%   $259.7511   $259.75   $259.75   $259.80  
  Purchase #2 $232.82   12.665%   $262.3067   $262.31   $262.30   $262.30  
  Purchase #3 $183.65   10.313%   $202.5898   $202.59   $202.60   $202.60  
  Purchase #4 $144.69   3.182%   $149.294   $149.29   $149.30   $149.30  
  Purchase #5 $49.40   6.471%   $52.5967   $52.60   $52.60   $52.60  
  Purchase #6 $141.63   13.139%   $160.2388   $160.24   $160.25   $160.20  
  Purchase #7 $22.73   6.401%   $24.1849   $24.18   $24.20   $24.20  
  7 purchase totals = $1,013.55       $1,110.9620   $1,110.96   $1,111.00   $1,111.00