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 $89.48   6.284%   $95.1029   $95.10   $95.10   $95.10  
  Purchase #2 $202.75   8.256%   $219.489   $219.49   $219.50   $219.50  
  Purchase #3 $49.48   8.252%   $53.5631   $53.56   $53.55   $53.60  
  Purchase #4 $193.85   9.189%   $211.6629   $211.66   $211.65   $211.70  
  Purchase #5 $87.65   9.506%   $95.982   $95.98   $96.00   $96.00  
  Purchase #6 $61.92   8.569%   $67.2259   $67.23   $67.25   $67.20  
  Purchase #7 $151.94   12.629%   $171.1285   $171.13   $171.15   $171.10  
  7 purchase totals = $837.07       $914.1543   $914.15   $914.20   $914.20