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	$134.73	5.435%	$142.0526	$142.05	$142.05	$142.10
Purchase #2	$134.64	8.156%	$145.6212	$145.62	$145.60	$145.60
Purchase #3	$11.46	11.500%	$12.7779	$12.78	$12.80	$12.80
Purchase #4	$97.43	9.729%	$106.909	$106.91	$106.90	$106.90
Purchase #5	$52.55	3.473%	$54.3751	$54.38	$54.40	$54.40
Purchase #6	$61.27	6.698%	$65.3739	$65.37	$65.35	$65.40
Purchase #7	$34.78	7.793%	$37.4904	$37.49	$37.50	$37.50
7 purchase totals =	$526.86		$564.6001	$564.60	$564.60	$564.70