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 $211.52   10.486%   $233.7   $233.70   $233.70   $233.70  
  Purchase #2 $93.94   13.421%   $106.5477   $106.55   $106.55   $106.50  
  Purchase #3 $221.83   13.520%   $251.8214   $251.82   $251.80   $251.80  
  Purchase #4 $51.49   13.476%   $58.4288   $58.43   $58.45   $58.40  
  Purchase #5 $215.30   5.214%   $226.5257   $226.53   $226.55   $226.50  
  Purchase #6 $194.50   4.224%   $202.7157   $202.72   $202.70   $202.70  
  Purchase #7 $82.81   13.827%   $94.2601   $94.26   $94.25   $94.30  
  7 purchase totals = $1,071.39       $1,173.9994   $1,174.01   $1,174.00   $1,173.90