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 $194.60   10.611%   $215.249   $215.25   $215.25   $215.20  
  Purchase #2 $241.40   4.364%   $251.9347   $251.93   $251.95   $251.90  
  Purchase #3 $66.27   3.803%   $68.7902   $68.79   $68.80   $68.80  
  Purchase #4 $79.52   4.220%   $82.8757   $82.88   $82.90   $82.90  
  Purchase #5 $62.59   13.267%   $70.8938   $70.89   $70.90   $70.90  
  Purchase #6 $241.70   3.578%   $250.348   $250.35   $250.35   $250.30  
  Purchase #7 $189.84   8.740%   $206.432   $206.43   $206.45   $206.40  
  7 purchase totals = $1,075.92       $1,146.5234   $1,146.52   $1,146.60   $1,146.40