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 $116.50   11.250%   $129.6063   $129.61   $129.60   $129.60  
  Purchase #2 $79.52   3.120%   $82.001   $82.00   $82.00   $82.00  
  Purchase #3 $93.35   9.794%   $102.4927   $102.49   $102.50   $102.50  
  Purchase #4 $201.61   12.109%   $226.023   $226.02   $226.00   $226.00  
  Purchase #5 $47.49   9.643%   $52.0695   $52.07   $52.05   $52.10  
  Purchase #6 $186.36   10.277%   $205.5122   $205.51   $205.50   $205.50  
  Purchase #7 $242.92   5.629%   $256.594   $256.59   $256.60   $256.60  
  7 purchase totals = $967.75       $1,054.2987   $1,054.29   $1,054.25   $1,054.30