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 $147.30   4.397%   $153.7768   $153.78   $153.80   $153.80  
  Purchase #2 $198.55   4.422%   $207.3299   $207.33   $207.35   $207.30  
  Purchase #3 $37.49   11.426%   $41.7736   $41.77   $41.75   $41.80  
  Purchase #4 $203.74   10.569%   $225.2733   $225.27   $225.25   $225.30  
  Purchase #5 $24.55   8.568%   $26.6534   $26.65   $26.65   $26.70  
  Purchase #6 $5.49   11.567%   $6.125   $6.13   $6.15   $6.10  
  Purchase #7 $214.39   9.274%   $234.2725   $234.27   $234.25   $234.30  
  7 purchase totals = $831.51       $895.2045   $895.20   $895.20   $895.30