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 $59.34   9.868%   $65.1957   $65.20   $65.20   $65.20  
  Purchase #2 $216.65   9.540%   $237.3184   $237.32   $237.30   $237.30  
  Purchase #3 $116.57   13.466%   $132.2673   $132.27   $132.25   $132.30  
  Purchase #4 $186.38   5.135%   $195.9506   $195.95   $195.95   $196.00  
  Purchase #5 $184.63   11.470%   $205.8071   $205.81   $205.80   $205.80  
  Purchase #6 $68.44   7.512%   $73.5812   $73.58   $73.60   $73.60  
  Purchase #7 $194.68   12.243%   $218.5147   $218.51   $218.50   $218.50  
  7 purchase totals = $1,026.69       $1,128.6350   $1,128.64   $1,128.60   $1,128.70