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 $90.83   4.625%   $95.0309   $95.03   $95.05   $95.00  
  Purchase #2 $197.52   6.655%   $210.665   $210.67   $210.65   $210.70  
  Purchase #3 $220.79   9.730%   $242.2729   $242.27   $242.25   $242.30  
  Purchase #4 $200.45   4.385%   $209.2397   $209.24   $209.25   $209.20  
  Purchase #5 $239.34   5.128%   $251.6134   $251.61   $251.60   $251.60  
  Purchase #6 $184.95   12.291%   $207.6822   $207.68   $207.70   $207.70  
  Purchase #7 $46.85   7.586%   $50.404   $50.40   $50.40   $50.40  
  7 purchase totals = $1,180.73       $1,266.9081   $1,266.90   $1,266.90   $1,266.90