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 $98.76   3.871%   $102.583   $102.58   $102.60   $102.60  
  Purchase #2 $180.65   8.109%   $195.2989   $195.30   $195.30   $195.30  
  Purchase #3 $113.69   13.369%   $128.8892   $128.89   $128.90   $128.90  
  Purchase #4 $71.74   5.383%   $75.6018   $75.60   $75.60   $75.60  
  Purchase #5 $200.59   6.115%   $212.8561   $212.86   $212.85   $212.90  
  Purchase #6 $158.53   11.196%   $176.279   $176.28   $176.30   $176.30  
  Purchase #7 $153.99   11.262%   $171.3324   $171.33   $171.35   $171.30  
  7 purchase totals = $977.95       $1,062.8404   $1,062.84   $1,062.90   $1,062.90