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 $246.62   9.363%   $269.711   $269.71   $269.70   $269.70  
  Purchase #2 $217.33   13.435%   $246.5283   $246.53   $246.55   $246.50  
  Purchase #3 $32.51   3.277%   $33.5754   $33.58   $33.60   $33.60  
  Purchase #4 $48.69   11.401%   $54.2411   $54.24   $54.25   $54.20  
  Purchase #5 $154.53   7.283%   $165.7844   $165.78   $165.80   $165.80  
  Purchase #6 $161.92   9.556%   $177.3931   $177.39   $177.40   $177.40  
  Purchase #7 $199.25   5.402%   $210.0135   $210.01   $210.00   $210.00  
  7 purchase totals = $1,060.85       $1,157.2468   $1,157.24   $1,157.30   $1,157.20