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 $216.93   7.846%   $233.9503   $233.95   $233.95   $234.00  
  Purchase #2 $208.62   8.648%   $226.6615   $226.66   $226.65   $226.70  
  Purchase #3 $28.34   13.651%   $32.2087   $32.21   $32.20   $32.20  
  Purchase #4 $187.89   11.689%   $209.8525   $209.85   $209.85   $209.90  
  Purchase #5 $117.74   7.135%   $126.1407   $126.14   $126.15   $126.10  
  Purchase #6 $60.98   3.333%   $63.0125   $63.01   $63.00   $63.00  
  Purchase #7 $52.30   11.751%   $58.4458   $58.45   $58.45   $58.40  
  7 purchase totals = $872.80       $950.2720   $950.27   $950.25   $950.30