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 $56.58   9.391%   $61.8934   $61.89   $61.90   $61.90  
  Purchase #2 $149.94   8.567%   $162.7854   $162.79   $162.80   $162.80  
  Purchase #3 $217.91   11.746%   $243.5057   $243.51   $243.50   $243.50  
  Purchase #4 $22.25   13.401%   $25.2317   $25.23   $25.25   $25.20  
  Purchase #5 $215.89   6.397%   $229.7005   $229.70   $229.70   $229.70  
  Purchase #6 $212.94   5.349%   $224.3302   $224.33   $224.35   $224.30  
  Purchase #7 $249.42   11.451%   $277.9811   $277.98   $278.00   $278.00  
  7 purchase totals = $1,124.93       $1,225.4280   $1,225.43   $1,225.50   $1,225.40