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	$58.43	6.123%	$62.0077	$62.01	$62.00	$62.00
Purchase #2	$96.43	6.163%	$102.373	$102.37	$102.35	$102.40
Purchase #3	$183.76	3.338%	$189.8939	$189.89	$189.90	$189.90
Purchase #4	$85.50	6.189%	$90.7916	$90.79	$90.80	$90.80
Purchase #5	$131.87	11.107%	$146.5168	$146.52	$146.50	$146.50
Purchase #6	$134.91	7.157%	$144.5655	$144.57	$144.55	$144.60
Purchase #7	$212.76	12.168%	$238.6486	$238.65	$238.65	$238.60
7 purchase totals =	$903.66		$974.7971	$974.80	$974.75	$974.80