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 $41.33   5.313%   $43.5259   $43.53   $43.55   $43.50  
  Purchase #2 $150.28   5.435%   $158.4477   $158.45   $158.45   $158.40  
  Purchase #3 $93.82   3.461%   $97.0671   $97.07   $97.05   $97.10  
  Purchase #4 $95.33   4.810%   $99.9154   $99.92   $99.90   $99.90  
  Purchase #5 $23.80   4.606%   $24.8962   $24.90   $24.90   $24.90  
  Purchase #6 $196.59   6.608%   $209.5807   $209.58   $209.60   $209.60  
  Purchase #7 $188.60   6.620%   $201.0853   $201.09   $201.10   $201.10  
  7 purchase totals = $789.75       $834.5183   $834.54   $834.55   $834.50