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 $183.81   8.277%   $199.024   $199.02   $199.00   $199.00  
  Purchase #2 $243.94   7.174%   $261.4403   $261.44   $261.45   $261.40  
  Purchase #3 $218.48   11.283%   $243.1311   $243.13   $243.15   $243.10  
  Purchase #4 $152.49   11.426%   $169.9135   $169.91   $169.90   $169.90  
  Purchase #5 $119.68   3.254%   $123.5744   $123.57   $123.55   $123.60  
  Purchase #6 $54.68   6.867%   $58.4349   $58.43   $58.45   $58.40  
  Purchase #7 $76.45   5.268%   $80.4774   $80.48   $80.50   $80.50  
  7 purchase totals = $1,049.53       $1,135.9956   $1,135.98   $1,136.00   $1,135.90