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	$67.46	10.479%	$74.5291	$74.53	$74.55	$74.50
Purchase #2	$196.35	8.530%	$213.0987	$213.10	$213.10	$213.10
Purchase #3	$123.36	6.138%	$130.9318	$130.93	$130.95	$130.90
Purchase #4	$46.54	3.690%	$48.2573	$48.26	$48.25	$48.30
Purchase #5	$124.50	5.715%	$131.6152	$131.62	$131.60	$131.60
Purchase #6	$62.86	5.827%	$66.5229	$66.52	$66.50	$66.50
Purchase #7	$30.33	4.231%	$31.6133	$31.61	$31.60	$31.60
7 purchase totals =	$651.40		$696.5683	$696.57	$696.55	$696.50