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 $208.91   11.772%   $233.5029   $233.50   $233.50   $233.50  
  Purchase #2 $219.35   8.771%   $238.5892   $238.59   $238.60   $238.60  
  Purchase #3 $245.46   9.856%   $269.6525   $269.65   $269.65   $269.70  
  Purchase #4 $37.90   9.270%   $41.4133   $41.41   $41.40   $41.40  
  Purchase #5 $39.86   8.720%   $43.3358   $43.34   $43.35   $43.30  
  Purchase #6 $116.40   8.315%   $126.0787   $126.08   $126.10   $126.10  
  Purchase #7 $191.68   5.744%   $202.6901   $202.69   $202.70   $202.70  
  7 purchase totals = $1,059.56       $1,155.2625   $1,155.26   $1,155.30   $1,155.30