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 $208.26   3.776%   $216.1239   $216.12   $216.10   $216.10  
  Purchase #2 $246.53   11.299%   $274.3854   $274.39   $274.40   $274.40  
  Purchase #3 $87.26   8.843%   $94.9764   $94.98   $95.00   $95.00  
  Purchase #4 $206.58   9.304%   $225.8002   $225.80   $225.80   $225.80  
  Purchase #5 $176.87   7.302%   $189.785   $189.79   $189.80   $189.80  
  Purchase #6 $11.25   13.262%   $12.742   $12.74   $12.75   $12.70  
  Purchase #7 $10.44   13.482%   $11.8475   $11.85   $11.85   $11.80  
  7 purchase totals = $947.19       $1,025.6604   $1,025.67   $1,025.70   $1,025.60