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 $192.98   13.494%   $219.0207   $219.02   $219.00   $219.00  
  Purchase #2 $174.34   3.791%   $180.9492   $180.95   $180.95   $180.90  
  Purchase #3 $233.83   13.219%   $264.74   $264.74   $264.75   $264.70  
  Purchase #4 $160.26   3.803%   $166.3547   $166.35   $166.35   $166.40  
  Purchase #5 $177.79   7.588%   $191.2807   $191.28   $191.30   $191.30  
  Purchase #6 $222.66   10.270%   $245.5272   $245.53   $245.55   $245.50  
  Purchase #7 $207.67   5.309%   $218.6952   $218.70   $218.70   $218.70  
  7 purchase totals = $1,369.53       $1,486.5677   $1,486.57   $1,486.60   $1,486.50