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	$102.59	8.282%	$111.0865	$111.09	$111.10	$111.10
Purchase #2	$138.89	8.752%	$151.0457	$151.05	$151.05	$151.00
Purchase #3	$222.84	11.172%	$247.7357	$247.74	$247.75	$247.70
Purchase #4	$112.87	5.510%	$119.0891	$119.09	$119.10	$119.10
Purchase #5	$236.36	13.821%	$269.0273	$269.03	$269.05	$269.00
Purchase #6	$88.87	12.200%	$99.7121	$99.71	$99.70	$99.70
Purchase #7	$20.46	4.774%	$21.4368	$21.44	$21.45	$21.40
7 purchase totals =	$922.88		$1,019.1332	$1,019.15	$1,019.20	$1,019.00