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	$200.59	10.804%	$222.2617	$222.26	$222.25	$222.30
Purchase #2	$80.99	4.671%	$84.773	$84.77	$84.75	$84.80
Purchase #3	$250.74	3.141%	$258.6157	$258.62	$258.60	$258.60
Purchase #4	$237.93	12.762%	$268.2946	$268.29	$268.30	$268.30
Purchase #5	$166.60	4.166%	$173.5406	$173.54	$173.55	$173.50
Purchase #6	$180.71	5.397%	$190.4629	$190.46	$190.45	$190.50
Purchase #7	$61.38	9.281%	$67.0767	$67.08	$67.10	$67.10
7 purchase totals =	$1,178.94		$1,265.0252	$1,265.02	$1,265.00	$1,265.10