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 $47.92   10.526%   $52.9641   $52.96   $52.95   $53.00  
  Purchase #2 $208.80   10.363%   $230.4379   $230.44   $230.45   $230.40  
  Purchase #3 $204.45   4.487%   $213.6237   $213.62   $213.60   $213.60  
  Purchase #4 $50.44   13.768%   $57.3846   $57.38   $57.40   $57.40  
  Purchase #5 $171.82   6.523%   $183.0278   $183.03   $183.05   $183.00  
  Purchase #6 $202.86   6.306%   $215.6524   $215.65   $215.65   $215.70  
  Purchase #7 $68.95   5.288%   $72.5961   $72.60   $72.60   $72.60  
  7 purchase totals = $955.24       $1,025.6866   $1,025.68   $1,025.70   $1,025.70