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 $66.93   11.559%   $74.6664   $74.67   $74.65   $74.70  
  Purchase #2 $189.64   6.599%   $202.1543   $202.15   $202.15   $202.20  
  Purchase #3 $182.67   6.751%   $195.0021   $195.00   $195.00   $195.00  
  Purchase #4 $239.70   11.489%   $267.2391   $267.24   $267.25   $267.20  
  Purchase #5 $127.35   12.608%   $143.4063   $143.41   $143.40   $143.40  
  Purchase #6 $38.95   12.865%   $43.9609   $43.96   $43.95   $44.00  
  Purchase #7 $142.71   4.779%   $149.5301   $149.53   $149.55   $149.50  
  7 purchase totals = $987.95       $1,075.9592   $1,075.96   $1,075.95   $1,076.00