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 $86.66   8.109%   $93.6873   $93.69   $93.70   $93.70  
  Purchase #2 $58.64   6.314%   $62.3425   $62.34   $62.35   $62.30  
  Purchase #3 $148.52   4.459%   $155.1425   $155.14   $155.15   $155.10  
  Purchase #4 $200.59   11.335%   $223.3269   $223.33   $223.35   $223.30  
  Purchase #5 $193.99   4.277%   $202.287   $202.29   $202.30   $202.30  
  Purchase #6 $198.72   6.137%   $210.9154   $210.92   $210.90   $210.90  
  Purchase #7 $217.94   13.167%   $246.6362   $246.64   $246.65   $246.60  
  7 purchase totals = $1,105.06       $1,194.3378   $1,194.35   $1,194.40   $1,194.20