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 $94.52   4.377%   $98.6571   $98.66   $98.65   $98.70  
  Purchase #2 $231.45   8.129%   $250.2646   $250.26   $250.25   $250.30  
  Purchase #3 $145.87   3.770%   $151.3693   $151.37   $151.35   $151.40  
  Purchase #4 $211.30   9.147%   $230.6276   $230.63   $230.65   $230.60  
  Purchase #5 $51.70   6.747%   $55.1882   $55.19   $55.20   $55.20  
  Purchase #6 $212.58   6.560%   $226.5252   $226.53   $226.55   $226.50  
  Purchase #7 $126.39   12.279%   $141.9094   $141.91   $141.90   $141.90  
  7 purchase totals = $1,073.81       $1,154.5414   $1,154.55   $1,154.55   $1,154.60