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	$192.73	13.471%	$218.6927	$218.69	$218.70	$218.70
Purchase #2	$232.38	9.537%	$254.5421	$254.54	$254.55	$254.50
Purchase #3	$213.41	4.500%	$223.0135	$223.01	$223.00	$223.00
Purchase #4	$69.93	10.697%	$77.4104	$77.41	$77.40	$77.40
Purchase #5	$112.27	3.580%	$116.2893	$116.29	$116.30	$116.30
Purchase #6	$38.43	5.202%	$40.4291	$40.43	$40.45	$40.40
Purchase #7	$73.47	10.451%	$81.1483	$81.15	$81.15	$81.10
7 purchase totals =	$932.62		$1,011.5254	$1,011.52	$1,011.55	$1,011.40