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	$125.43	9.519%	$137.3697	$137.37	$137.35	$137.40
Purchase #2	$45.89	4.229%	$47.8307	$47.83	$47.85	$47.80
Purchase #3	$65.55	6.160%	$69.5879	$69.59	$69.60	$69.60
Purchase #4	$179.52	5.873%	$190.0632	$190.06	$190.05	$190.10
Purchase #5	$99.52	5.623%	$105.116	$105.12	$105.10	$105.10
Purchase #6	$103.91	6.139%	$110.289	$110.29	$110.30	$110.30
Purchase #7	$60.33	8.133%	$65.2366	$65.24	$65.25	$65.20
7 purchase totals =	$680.15		$725.4931	$725.50	$725.50	$725.50