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	$52.50	6.363%	$55.8406	$55.84	$55.85	$55.80
Purchase #2	$244.36	5.537%	$257.8902	$257.89	$257.90	$257.90
Purchase #3	$54.92	13.565%	$62.3699	$62.37	$62.35	$62.40
Purchase #4	$192.25	4.453%	$200.8109	$200.81	$200.80	$200.80
Purchase #5	$98.57	13.243%	$111.6236	$111.62	$111.60	$111.60
Purchase #6	$137.78	7.157%	$147.6409	$147.64	$147.65	$147.60
Purchase #7	$226.34	5.215%	$238.1436	$238.14	$238.15	$238.10
7 purchase totals =	$1,006.72		$1,074.3197	$1,074.31	$1,074.30	$1,074.20