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	$58.42	7.503%	$62.8033	$62.80	$62.80	$62.80
Purchase #2	$13.45	6.656%	$14.3452	$14.35	$14.35	$14.30
Purchase #3	$94.70	6.141%	$100.5155	$100.52	$100.50	$100.50
Purchase #4	$172.73	11.420%	$192.4558	$192.46	$192.45	$192.50
Purchase #5	$228.41	4.277%	$238.1791	$238.18	$238.20	$238.20
Purchase #6	$187.26	3.734%	$194.2523	$194.25	$194.25	$194.30
Purchase #7	$71.79	12.680%	$80.893	$80.89	$80.90	$80.90
7 purchase totals =	$826.76		$883.4442	$883.45	$883.45	$883.50