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	$238.25	10.450%	$263.1471	$263.15	$263.15	$263.10
Purchase #2	$67.65	12.561%	$76.1475	$76.15	$76.15	$76.10
Purchase #3	$53.98	3.767%	$56.0134	$56.01	$56.00	$56.00
Purchase #4	$34.62	8.176%	$37.4505	$37.45	$37.45	$37.50
Purchase #5	$117.84	8.449%	$127.7963	$127.80	$127.80	$127.80
Purchase #6	$210.30	6.302%	$223.5531	$223.55	$223.55	$223.60
Purchase #7	$213.58	4.742%	$223.708	$223.71	$223.70	$223.70
7 purchase totals =	$936.22		$1,007.8159	$1,007.82	$1,007.80	$1,007.80