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	$246.41	3.782%	$255.7292	$255.73	$255.75	$255.70
Purchase #2	$11.79	10.418%	$13.0183	$13.02	$13.00	$13.00
Purchase #3	$107.43	4.109%	$111.8443	$111.84	$111.85	$111.80
Purchase #4	$98.25	12.688%	$110.716	$110.72	$110.70	$110.70
Purchase #5	$106.82	6.366%	$113.6202	$113.62	$113.60	$113.60
Purchase #6	$197.42	7.192%	$211.6184	$211.62	$211.60	$211.60
Purchase #7	$134.57	12.488%	$151.3751	$151.38	$151.40	$151.40
7 purchase totals =	$902.69		$967.9215	$967.93	$967.90	$967.80