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 $218.77   7.214%   $234.5521   $234.55   $234.55   $234.60  
  Purchase #2 $225.62   6.504%   $240.2943   $240.29   $240.30   $240.30  
  Purchase #3 $84.33   13.642%   $95.8343   $95.83   $95.85   $95.80  
  Purchase #4 $50.87   5.633%   $53.7355   $53.74   $53.75   $53.70  
  Purchase #5 $184.55   13.339%   $209.1671   $209.17   $209.15   $209.20  
  Purchase #6 $193.56   4.742%   $202.7386   $202.74   $202.75   $202.70  
  Purchase #7 $24.78   6.458%   $26.3803   $26.38   $26.40   $26.40  
  7 purchase totals = $982.48       $1,062.7022   $1,062.70   $1,062.75   $1,062.70