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 $195.57   9.688%   $214.5168   $214.52   $214.50   $214.50  
  Purchase #2 $97.29   9.494%   $106.5267   $106.53   $106.55   $106.50  
  Purchase #3 $49.38   8.649%   $53.6509   $53.65   $53.65   $53.70  
  Purchase #4 $50.91   11.571%   $56.8008   $56.80   $56.80   $56.80  
  Purchase #5 $129.32   4.860%   $135.605   $135.61   $135.60   $135.60  
  Purchase #6 $31.55   8.162%   $34.1251   $34.13   $34.15   $34.10  
  Purchase #7 $99.64   11.392%   $110.991   $110.99   $111.00   $111.00  
  7 purchase totals = $653.66       $712.2163   $712.23   $712.25   $712.20