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 $209.39   4.759%   $219.3549   $219.35   $219.35   $219.40  
  Purchase #2 $172.67   13.861%   $196.6038   $196.60   $196.60   $196.60  
  Purchase #3 $56.52   11.850%   $63.2176   $63.22   $63.20   $63.20  
  Purchase #4 $198.65   6.229%   $211.0239   $211.02   $211.00   $211.00  
  Purchase #5 $244.94   11.577%   $273.2967   $273.30   $273.30   $273.30  
  Purchase #6 $245.55   5.582%   $259.2566   $259.26   $259.25   $259.30  
  Purchase #7 $177.53   13.758%   $201.9546   $201.95   $201.95   $202.00  
  7 purchase totals = $1,305.25       $1,424.7081   $1,424.70   $1,424.65   $1,424.80