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	$200.74	11.480%	$223.785	$223.79	$223.80	$223.80
Purchase #2	$248.83	8.335%	$269.57	$269.57	$269.55	$269.60
Purchase #3	$16.79	9.162%	$18.3283	$18.33	$18.35	$18.30
Purchase #4	$246.54	13.586%	$280.0349	$280.03	$280.05	$280.00
Purchase #5	$18.83	3.618%	$19.5113	$19.51	$19.50	$19.50
Purchase #6	$223.31	3.478%	$231.0767	$231.08	$231.10	$231.10
Purchase #7	$53.95	5.441%	$56.8854	$56.89	$56.90	$56.90
7 purchase totals =	$1,008.99		$1,099.1916	$1,099.20	$1,099.25	$1,099.20