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 $206.97   11.182%   $230.1134   $230.11   $230.10   $230.10  
  Purchase #2 $157.31   11.812%   $175.8915   $175.89   $175.90   $175.90  
  Purchase #3 $44.84   12.644%   $50.5096   $50.51   $50.50   $50.50  
  Purchase #4 $217.35   11.152%   $241.5889   $241.59   $241.60   $241.60  
  Purchase #5 $87.77   9.616%   $96.21   $96.21   $96.20   $96.20  
  Purchase #6 $83.50   3.501%   $86.4233   $86.42   $86.40   $86.40  
  Purchase #7 $165.30   5.172%   $173.8493   $173.85   $173.85   $173.80  
  7 purchase totals = $963.04       $1,054.5860   $1,054.58   $1,054.55   $1,054.50