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 $194.33   10.607%   $214.9426   $214.94   $214.95   $214.90  
  Purchase #2 $86.42   12.347%   $97.0903   $97.09   $97.10   $97.10  
  Purchase #3 $52.91   7.350%   $56.7989   $56.80   $56.80   $56.80  
  Purchase #4 $158.53   5.346%   $167.005   $167.01   $167.00   $167.00  
  Purchase #5 $25.82   8.846%   $28.104   $28.10   $28.10   $28.10  
  Purchase #6 $128.51   6.129%   $136.3864   $136.39   $136.40   $136.40  
  Purchase #7 $50.27   8.631%   $54.6088   $54.61   $54.60   $54.60  
  7 purchase totals = $696.79       $754.9360   $754.94   $754.95   $754.90