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 $92.57   4.295%   $96.5459   $96.55   $96.55   $96.50  
  Purchase #2 $72.48   11.606%   $80.892   $80.89   $80.90   $80.90  
  Purchase #3 $8.48   13.842%   $9.6538   $9.65   $9.65   $9.70  
  Purchase #4 $53.59   3.448%   $55.4378   $55.44   $55.45   $55.40  
  Purchase #5 $72.30   7.369%   $77.6278   $77.63   $77.65   $77.60  
  Purchase #6 $64.81   3.836%   $67.2961   $67.30   $67.30   $67.30  
  Purchase #7 $52.79   11.506%   $58.864   $58.86   $58.85   $58.90  
  7 purchase totals = $417.02       $446.3174   $446.32   $446.35   $446.30