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 $129.59   9.283%   $141.6198   $141.62   $141.60   $141.60  
  Purchase #2 $227.68   8.254%   $246.4727   $246.47   $246.45   $246.50  
  Purchase #3 $111.43   3.726%   $115.5819   $115.58   $115.60   $115.60  
  Purchase #4 $38.93   5.217%   $40.961   $40.96   $40.95   $41.00  
  Purchase #5 $191.81   10.342%   $211.647   $211.65   $211.65   $211.60  
  Purchase #6 $175.40   9.143%   $191.4368   $191.44   $191.45   $191.40  
  Purchase #7 $146.85   13.310%   $166.3957   $166.40   $166.40   $166.40  
  7 purchase totals = $1,021.69       $1,114.1149   $1,114.12   $1,114.10   $1,114.10