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	$64.99	9.395%	$71.0958	$71.10	$71.10	$71.10
Purchase #2	$111.94	10.192%	$123.3489	$123.35	$123.35	$123.30
Purchase #3	$215.71	11.712%	$240.974	$240.97	$240.95	$241.00
Purchase #4	$49.45	7.712%	$53.2636	$53.26	$53.25	$53.30
Purchase #5	$109.88	4.263%	$114.5642	$114.56	$114.55	$114.60
Purchase #6	$149.53	11.727%	$167.0654	$167.07	$167.05	$167.10
Purchase #7	$13.79	12.207%	$15.4733	$15.47	$15.45	$15.50
7 purchase totals =	$715.29		$785.7852	$785.78	$785.70	$785.90