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 $41.92   10.489%   $46.317   $46.32   $46.30   $46.30  
  Purchase #2 $224.80   6.821%   $240.1336   $240.13   $240.15   $240.10  
  Purchase #3 $229.87   6.649%   $245.1541   $245.15   $245.15   $245.20  
  Purchase #4 $215.33   7.392%   $231.2472   $231.25   $231.25   $231.20  
  Purchase #5 $48.99   5.235%   $51.5546   $51.55   $51.55   $51.60  
  Purchase #6 $36.82   7.776%   $39.6831   $39.68   $39.70   $39.70  
  Purchase #7 $165.92   7.382%   $178.1682   $178.17   $178.15   $178.20  
  7 purchase totals = $963.65       $1,032.2578   $1,032.25   $1,032.25   $1,032.30