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 $53.96   8.506%   $58.5498   $58.55   $58.55   $58.50  
  Purchase #2 $226.74   8.350%   $245.6728   $245.67   $245.65   $245.70  
  Purchase #3 $144.44   6.133%   $153.2985   $153.30   $153.30   $153.30  
  Purchase #4 $238.72   3.380%   $246.7887   $246.79   $246.80   $246.80  
  Purchase #5 $208.98   13.731%   $237.675   $237.68   $237.70   $237.70  
  Purchase #6 $100.88   12.348%   $113.3367   $113.34   $113.35   $113.30  
  Purchase #7 $147.97   7.400%   $158.9198   $158.92   $158.90   $158.90  
  7 purchase totals = $1,121.69       $1,214.2413   $1,214.25   $1,214.25   $1,214.20