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	$134.64	13.785%	$153.2001	$153.20	$153.20	$153.20
Purchase #2	$192.55	13.613%	$218.7618	$218.76	$218.75	$218.80
Purchase #3	$57.56	4.387%	$60.0852	$60.09	$60.10	$60.10
Purchase #4	$80.39	11.855%	$89.9202	$89.92	$89.90	$89.90
Purchase #5	$44.33	5.516%	$46.7752	$46.78	$46.80	$46.80
Purchase #6	$91.83	9.234%	$100.3096	$100.31	$100.30	$100.30
Purchase #7	$38.27	13.320%	$43.3676	$43.37	$43.35	$43.40
7 purchase totals =	$639.57		$712.4197	$712.43	$712.40	$712.50