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 $152.36   8.414%   $165.1796   $165.18   $165.20   $165.20  
  Purchase #2 $190.99   13.434%   $216.6476   $216.65   $216.65   $216.60  
  Purchase #3 $24.53   10.307%   $27.0583   $27.06   $27.05   $27.10  
  Purchase #4 $184.45   12.141%   $206.8441   $206.84   $206.85   $206.80  
  Purchase #5 $110.78   4.721%   $116.0099   $116.01   $116.00   $116.00  
  Purchase #6 $219.83   12.183%   $246.6119   $246.61   $246.60   $246.60  
  Purchase #7 $219.54   3.542%   $227.3161   $227.32   $227.30   $227.30  
  7 purchase totals = $1,102.48       $1,205.6675   $1,205.67   $1,205.65   $1,205.60