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 $69.62   5.280%   $73.2959   $73.30   $73.30   $73.30  
  Purchase #2 $168.77   10.638%   $186.7238   $186.72   $186.70   $186.70  
  Purchase #3 $192.61   13.850%   $219.2865   $219.29   $219.30   $219.30  
  Purchase #4 $189.49   11.669%   $211.6016   $211.60   $211.60   $211.60  
  Purchase #5 $160.29   9.642%   $175.7452   $175.75   $175.75   $175.70  
  Purchase #6 $160.80   6.255%   $170.858   $170.86   $170.85   $170.90  
  Purchase #7 $36.64   4.530%   $38.2998   $38.30   $38.30   $38.30  
  7 purchase totals = $978.22       $1,075.8108   $1,075.82   $1,075.80   $1,075.80