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	$50.90	11.414%	$56.7097	$56.71	$56.70	$56.70
Purchase #2	$169.33	13.545%	$192.2657	$192.27	$192.25	$192.30
Purchase #3	$182.78	4.698%	$191.367	$191.37	$191.35	$191.40
Purchase #4	$40.60	3.859%	$42.1668	$42.17	$42.15	$42.20
Purchase #5	$222.52	3.826%	$231.0336	$231.03	$231.05	$231.00
Purchase #6	$92.75	4.120%	$96.5713	$96.57	$96.55	$96.60
Purchase #7	$204.69	8.158%	$221.3886	$221.39	$221.40	$221.40
7 purchase totals =	$963.57		$1,031.5027	$1,031.51	$1,031.45	$1,031.60