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	$140.32	13.262%	$158.9292	$158.93	$158.95	$158.90
Purchase #2	$162.72	5.171%	$171.1343	$171.13	$171.15	$171.10
Purchase #3	$214.54	3.806%	$222.7054	$222.71	$222.70	$222.70
Purchase #4	$154.65	12.166%	$173.4647	$173.46	$173.45	$173.50
Purchase #5	$142.81	13.129%	$161.5595	$161.56	$161.55	$161.60
Purchase #6	$7.41	4.487%	$7.7425	$7.74	$7.75	$7.70
Purchase #7	$170.93	12.316%	$191.9817	$191.98	$192.00	$192.00
7 purchase totals =	$993.38		$1,087.5173	$1,087.51	$1,087.55	$1,087.50