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 $195.65   3.529%   $202.5545   $202.55   $202.55   $202.60  
  Purchase #2 $110.51   3.344%   $114.2055   $114.21   $114.20   $114.20  
  Purchase #3 $243.59   3.105%   $251.1535   $251.15   $251.15   $251.20  
  Purchase #4 $205.71   6.266%   $218.5998   $218.60   $218.60   $218.60  
  Purchase #5 $41.86   13.437%   $47.4847   $47.48   $47.50   $47.50  
  Purchase #6 $21.63   11.469%   $24.1107   $24.11   $24.10   $24.10  
  Purchase #7 $167.37   7.592%   $180.0767   $180.08   $180.10   $180.10  
  7 purchase totals = $986.32       $1,038.1854   $1,038.18   $1,038.20   $1,038.30