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 $192.78   6.835%   $205.9565   $205.96   $205.95   $206.00  
  Purchase #2 $217.44   4.463%   $227.1443   $227.14   $227.15   $227.10  
  Purchase #3 $224.26   5.644%   $236.9172   $236.92   $236.90   $236.90  
  Purchase #4 $31.74   3.575%   $32.8747   $32.87   $32.85   $32.90  
  Purchase #5 $240.64   3.705%   $249.5557   $249.56   $249.55   $249.60  
  Purchase #6 $64.92   6.562%   $69.1801   $69.18   $69.20   $69.20  
  Purchase #7 $51.53   5.804%   $54.5208   $54.52   $54.50   $54.50  
  7 purchase totals = $1,023.31       $1,076.1493   $1,076.15   $1,076.10   $1,076.20