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 $185.52   8.662%   $201.5897   $201.59   $201.60   $201.60  
  Purchase #2 $189.62   8.376%   $205.5026   $205.50   $205.50   $205.50  
  Purchase #3 $24.56   5.771%   $25.9774   $25.98   $26.00   $26.00  
  Purchase #4 $114.65   5.272%   $120.6943   $120.69   $120.70   $120.70  
  Purchase #5 $181.26   8.271%   $196.252   $196.25   $196.25   $196.30  
  Purchase #6 $20.47   11.854%   $22.8965   $22.90   $22.90   $22.90  
  Purchase #7 $107.36   4.615%   $112.3147   $112.31   $112.30   $112.30  
  7 purchase totals = $823.44       $885.2272   $885.22   $885.25   $885.30