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 $118.56   6.288%   $126.0151   $126.02   $126.00   $126.00  
  Purchase #2 $200.32   4.594%   $209.5227   $209.52   $209.50   $209.50  
  Purchase #3 $235.72   4.660%   $246.7046   $246.70   $246.70   $246.70  
  Purchase #4 $72.56   9.846%   $79.7043   $79.70   $79.70   $79.70  
  Purchase #5 $214.78   11.739%   $239.993   $239.99   $240.00   $240.00  
  Purchase #6 $87.74   12.821%   $98.9891   $98.99   $99.00   $99.00  
  Purchase #7 $104.45   10.581%   $115.5019   $115.50   $115.50   $115.50  
  7 purchase totals = $1,034.13       $1,116.4307   $1,116.42   $1,116.40   $1,116.40