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	$113.47	12.448%	$127.5947	$127.59	$127.60	$127.60
Purchase #2	$137.42	11.455%	$153.1615	$153.16	$153.15	$153.20
Purchase #3	$173.67	4.606%	$181.6692	$181.67	$181.65	$181.70
Purchase #4	$147.82	5.698%	$156.2428	$156.24	$156.25	$156.20
Purchase #5	$144.86	4.814%	$151.8336	$151.83	$151.85	$151.80
Purchase #6	$114.57	12.832%	$129.2716	$129.27	$129.25	$129.30
Purchase #7	$158.45	10.371%	$174.8828	$174.88	$174.90	$174.90
7 purchase totals =	$990.26		$1,074.6562	$1,074.64	$1,074.65	$1,074.70