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 $41.36   5.526%   $43.6456   $43.65   $43.65   $43.60  
  Purchase #2 $118.92   5.452%   $125.4035   $125.40   $125.40   $125.40  
  Purchase #3 $241.86   4.627%   $253.0509   $253.05   $253.05   $253.10  
  Purchase #4 $144.70   3.199%   $149.329   $149.33   $149.35   $149.30  
  Purchase #5 $51.44   3.279%   $53.1267   $53.13   $53.15   $53.10  
  Purchase #6 $161.92   11.298%   $180.2137   $180.21   $180.20   $180.20  
  Purchase #7 $181.44   8.170%   $196.2636   $196.26   $196.25   $196.30  
  7 purchase totals = $941.64       $1,001.0330   $1,001.03   $1,001.05   $1,001.00