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 $176.58   9.330%   $193.0549   $193.05   $193.05   $193.10  
  Purchase #2 $217.27   13.644%   $246.9143   $246.91   $246.90   $246.90  
  Purchase #3 $103.96   13.520%   $118.0154   $118.02   $118.00   $118.00  
  Purchase #4 $189.62   6.147%   $201.2759   $201.28   $201.30   $201.30  
  Purchase #5 $222.85   5.497%   $235.1001   $235.10   $235.10   $235.10  
  Purchase #6 $112.63   6.509%   $119.9611   $119.96   $119.95   $120.00  
  Purchase #7 $219.57   9.747%   $240.9715   $240.97   $240.95   $241.00  
  7 purchase totals = $1,242.48       $1,355.2932   $1,355.29   $1,355.25   $1,355.40