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 $60.57   4.178%   $63.1006   $63.10   $63.10   $63.10  
  Purchase #2 $226.79   4.191%   $236.2948   $236.29   $236.30   $236.30  
  Purchase #3 $205.41   3.531%   $212.663   $212.66   $212.65   $212.70  
  Purchase #4 $204.85   13.548%   $232.6031   $232.60   $232.60   $232.60  
  Purchase #5 $107.60   9.156%   $117.4519   $117.45   $117.45   $117.50  
  Purchase #6 $85.30   9.168%   $93.1203   $93.12   $93.10   $93.10  
  Purchase #7 $113.76   6.754%   $121.4434   $121.44   $121.45   $121.40  
  7 purchase totals = $1,004.28       $1,076.6771   $1,076.66   $1,076.65   $1,076.70