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 $191.50   8.506%   $207.789   $207.79   $207.80   $207.80  
  Purchase #2 $186.36   5.611%   $196.8167   $196.82   $196.80   $196.80  
  Purchase #3 $69.82   9.212%   $76.2518   $76.25   $76.25   $76.30  
  Purchase #4 $110.80   4.497%   $115.7827   $115.78   $115.80   $115.80  
  Purchase #5 $67.92   12.585%   $76.4677   $76.47   $76.45   $76.50  
  Purchase #6 $142.82   3.363%   $147.623   $147.62   $147.60   $147.60  
  Purchase #7 $181.75   11.862%   $203.3092   $203.31   $203.30   $203.30  
  7 purchase totals = $950.97       $1,024.0401   $1,024.04   $1,024.00   $1,024.10