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	$54.72	13.473%	$62.0924	$62.09	$62.10	$62.10
Purchase #2	$241.85	9.439%	$264.6782	$264.68	$264.70	$264.70
Purchase #3	$154.96	6.118%	$164.4405	$164.44	$164.45	$164.40
Purchase #4	$250.31	10.321%	$276.1445	$276.14	$276.15	$276.10
Purchase #5	$87.25	13.142%	$98.7164	$98.72	$98.70	$98.70
Purchase #6	$74.79	3.256%	$77.2252	$77.23	$77.25	$77.20
Purchase #7	$103.39	8.703%	$112.388	$112.39	$112.40	$112.40
7 purchase totals =	$967.27		$1,055.6852	$1,055.69	$1,055.75	$1,055.60