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	$182.72	13.194%	$206.8281	$206.83	$206.85	$206.80
Purchase #2	$215.57	3.382%	$222.8606	$222.86	$222.85	$222.90
Purchase #3	$190.37	6.557%	$202.8526	$202.85	$202.85	$202.90
Purchase #4	$39.40	9.601%	$43.1828	$43.18	$43.20	$43.20
Purchase #5	$215.95	3.183%	$222.8237	$222.82	$222.80	$222.80
Purchase #6	$119.83	3.435%	$123.9462	$123.95	$123.95	$123.90
Purchase #7	$147.76	9.371%	$161.6066	$161.61	$161.60	$161.60
7 purchase totals =	$1,111.60		$1,184.1006	$1,184.10	$1,184.10	$1,184.10