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	$143.86	9.335%	$157.2893	$157.29	$157.30	$157.30
Purchase #2	$89.46	13.522%	$101.5568	$101.56	$101.55	$101.60
Purchase #3	$211.86	5.281%	$223.0483	$223.05	$223.05	$223.00
Purchase #4	$142.32	11.640%	$158.886	$158.89	$158.90	$158.90
Purchase #5	$228.93	10.407%	$252.7547	$252.75	$252.75	$252.80
Purchase #6	$58.53	6.696%	$62.4492	$62.45	$62.45	$62.40
Purchase #7	$50.67	4.620%	$53.011	$53.01	$53.00	$53.00
7 purchase totals =	$925.63		$1,008.9953	$1,009.00	$1,009.00	$1,009.00