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 $41.72   4.620%   $43.6475   $43.65   $43.65   $43.60  
  Purchase #2 $244.69   9.686%   $268.3907   $268.39   $268.40   $268.40  
  Purchase #3 $48.48   5.695%   $51.2409   $51.24   $51.25   $51.20  
  Purchase #4 $190.54   11.257%   $211.9891   $211.99   $212.00   $212.00  
  Purchase #5 $159.94   5.780%   $169.1845   $169.18   $169.20   $169.20  
  Purchase #6 $221.68   4.179%   $230.944   $230.94   $230.95   $230.90  
  Purchase #7 $172.61   7.760%   $186.0045   $186.00   $186.00   $186.00  
  7 purchase totals = $1,079.66       $1,161.4012   $1,161.39   $1,161.45   $1,161.30