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 $197.66   10.662%   $218.7345   $218.73   $218.75   $218.70  
  Purchase #2 $115.88   8.140%   $125.3126   $125.31   $125.30   $125.30  
  Purchase #3 $96.45   7.156%   $103.352   $103.35   $103.35   $103.40  
  Purchase #4 $46.70   6.846%   $49.8971   $49.90   $49.90   $49.90  
  Purchase #5 $152.28   11.405%   $169.6475   $169.65   $169.65   $169.60  
  Purchase #6 $107.25   12.706%   $120.8772   $120.88   $120.90   $120.90  
  Purchase #7 $218.57   3.764%   $226.797   $226.80   $226.80   $226.80  
  7 purchase totals = $934.79       $1,014.6179   $1,014.62   $1,014.65   $1,014.60