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 $124.74   13.520%   $141.6048   $141.60   $141.60   $141.60  
  Purchase #2 $96.46   5.866%   $102.1183   $102.12   $102.10   $102.10  
  Purchase #3 $161.77   3.525%   $167.4724   $167.47   $167.45   $167.50  
  Purchase #4 $224.57   7.436%   $241.269   $241.27   $241.25   $241.30  
  Purchase #5 $212.57   6.847%   $227.1247   $227.12   $227.10   $227.10  
  Purchase #6 $112.48   3.359%   $116.2582   $116.26   $116.25   $116.30  
  Purchase #7 $198.97   5.348%   $209.6109   $209.61   $209.60   $209.60  
  7 purchase totals = $1,131.56       $1,205.4583   $1,205.45   $1,205.35   $1,205.50