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	$56.72	5.694%	$59.9496	$59.95	$59.95	$59.90
Purchase #2	$93.74	12.210%	$105.1857	$105.19	$105.20	$105.20
Purchase #3	$140.36	9.784%	$154.0928	$154.09	$154.10	$154.10
Purchase #4	$150.81	12.850%	$170.1891	$170.19	$170.20	$170.20
Purchase #5	$40.28	7.571%	$43.3296	$43.33	$43.35	$43.30
Purchase #6	$39.58	5.231%	$41.6504	$41.65	$41.65	$41.70
Purchase #7	$158.72	5.144%	$166.8846	$166.88	$166.90	$166.90
7 purchase totals =	$680.21		$741.2818	$741.28	$741.35	$741.30