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 $56.81   11.329%   $63.246   $63.25   $63.25   $63.20  
  Purchase #2 $202.41   13.347%   $229.4257   $229.43   $229.45   $229.40  
  Purchase #3 $76.30   12.794%   $86.0618   $86.06   $86.05   $86.10  
  Purchase #4 $107.86   9.575%   $118.1876   $118.19   $118.20   $118.20  
  Purchase #5 $241.52   7.715%   $260.1533   $260.15   $260.15   $260.20  
  Purchase #6 $70.29   7.827%   $75.7916   $75.79   $75.80   $75.80  
  Purchase #7 $242.98   4.433%   $253.7513   $253.75   $253.75   $253.80  
  7 purchase totals = $998.17       $1,086.6173   $1,086.62   $1,086.65   $1,086.70