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 $157.86   3.232%   $162.962   $162.96   $162.95   $163.00  
  Purchase #2 $11.39   6.280%   $12.1053   $12.11   $12.10   $12.10  
  Purchase #3 $167.58   3.599%   $173.6112   $173.61   $173.60   $173.60  
  Purchase #4 $182.56   13.396%   $207.0157   $207.02   $207.00   $207.00  
  Purchase #5 $202.94   5.397%   $213.8927   $213.89   $213.90   $213.90  
  Purchase #6 $137.69   11.396%   $153.3812   $153.38   $153.40   $153.40  
  Purchase #7 $86.34   9.396%   $94.4525   $94.45   $94.45   $94.50  
  7 purchase totals = $946.36       $1,017.4206   $1,017.42   $1,017.40   $1,017.50