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 $153.47   13.354%   $173.9644   $173.96   $173.95   $174.00  
  Purchase #2 $205.25   10.831%   $227.4806   $227.48   $227.50   $227.50  
  Purchase #3 $13.61   5.599%   $14.372   $14.37   $14.35   $14.40  
  Purchase #4 $145.73   7.785%   $157.0751   $157.08   $157.10   $157.10  
  Purchase #5 $194.70   6.653%   $207.6534   $207.65   $207.65   $207.70  
  Purchase #6 $173.68   5.751%   $183.6683   $183.67   $183.65   $183.70  
  Purchase #7 $187.87   9.708%   $206.1084   $206.11   $206.10   $206.10  
  7 purchase totals = $1,074.31       $1,170.3222   $1,170.32   $1,170.30   $1,170.50