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 $145.53   5.357%   $153.326   $153.33   $153.35   $153.30  
  Purchase #2 $238.69   9.327%   $260.9526   $260.95   $260.95   $261.00  
  Purchase #3 $55.71   9.549%   $61.0297   $61.03   $61.05   $61.00  
  Purchase #4 $45.32   11.553%   $50.5558   $50.56   $50.55   $50.60  
  Purchase #5 $207.31   4.868%   $217.4019   $217.40   $217.40   $217.40  
  Purchase #6 $176.64   13.387%   $200.2868   $200.29   $200.30   $200.30  
  Purchase #7 $195.98   5.166%   $206.1043   $206.10   $206.10   $206.10  
  7 purchase totals = $1,065.18       $1,149.6571   $1,149.66   $1,149.70   $1,149.70