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	$207.45	10.391%	$229.0061	$229.01	$229.00	$229.00
Purchase #2	$98.62	4.200%	$102.762	$102.76	$102.75	$102.80
Purchase #3	$134.39	8.712%	$146.0981	$146.10	$146.10	$146.10
Purchase #4	$115.31	10.297%	$127.1835	$127.18	$127.20	$127.20
Purchase #5	$20.43	3.162%	$21.076	$21.08	$21.10	$21.10
Purchase #6	$102.91	11.632%	$114.8805	$114.88	$114.90	$114.90
Purchase #7	$151.40	4.631%	$158.4113	$158.41	$158.40	$158.40
7 purchase totals =	$830.51		$899.4175	$899.42	$899.45	$899.50