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 $60.26   3.436%   $62.3305   $62.33   $62.35   $62.30  
  Purchase #2 $207.27   7.689%   $223.207   $223.21   $223.20   $223.20  
  Purchase #3 $166.33   8.536%   $180.5279   $180.53   $180.55   $180.50  
  Purchase #4 $223.92   9.135%   $244.3751   $244.38   $244.40   $244.40  
  Purchase #5 $46.60   9.726%   $51.1323   $51.13   $51.15   $51.10  
  Purchase #6 $203.83   3.628%   $211.225   $211.23   $211.25   $211.20  
  Purchase #7 $25.63   8.523%   $27.8144   $27.81   $27.80   $27.80  
  7 purchase totals = $933.84       $1,000.6122   $1,000.62   $1,000.70   $1,000.50