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	$84.88	5.267%	$89.3506	$89.35	$89.35	$89.40
Purchase #2	$202.84	6.393%	$215.8076	$215.81	$215.80	$215.80
Purchase #3	$202.41	7.125%	$216.8317	$216.83	$216.85	$216.80
Purchase #4	$210.74	12.166%	$236.3786	$236.38	$236.40	$236.40
Purchase #5	$35.62	7.674%	$38.3535	$38.35	$38.35	$38.40
Purchase #6	$215.51	8.326%	$233.4534	$233.45	$233.45	$233.50
Purchase #7	$177.89	8.276%	$192.6122	$192.61	$192.60	$192.60
7 purchase totals =	$1,129.89		$1,222.7876	$1,222.78	$1,222.80	$1,222.90