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 $43.32   8.631%   $47.0589   $47.06   $47.05   $47.10  
  Purchase #2 $195.65   4.245%   $203.9553   $203.96   $203.95   $204.00  
  Purchase #3 $125.43   9.103%   $136.8479   $136.85   $136.85   $136.80  
  Purchase #4 $174.49   10.504%   $192.8184   $192.82   $192.80   $192.80  
  Purchase #5 $217.37   8.592%   $236.0464   $236.05   $236.05   $236.00  
  Purchase #6 $240.62   6.130%   $255.37   $255.37   $255.35   $255.40  
  Purchase #7 $201.86   4.206%   $210.3502   $210.35   $210.35   $210.40  
  7 purchase totals = $1,198.74       $1,282.4471   $1,282.46   $1,282.40   $1,282.50