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	$178.61	6.272%	$189.8124	$189.81	$189.80	$189.80
Purchase #2	$40.73	9.292%	$44.5146	$44.51	$44.50	$44.50
Purchase #3	$233.91	4.683%	$244.864	$244.86	$244.85	$244.90
Purchase #4	$223.32	12.274%	$250.7303	$250.73	$250.75	$250.70
Purchase #5	$102.87	13.612%	$116.8727	$116.87	$116.85	$116.90
Purchase #6	$183.65	3.236%	$189.5929	$189.59	$189.60	$189.60
Purchase #7	$228.63	11.753%	$255.5009	$255.50	$255.50	$255.50
7 purchase totals =	$1,191.72		$1,291.8878	$1,291.87	$1,291.85	$1,291.90