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	$211.94	5.650%	$223.9146	$223.91	$223.90	$223.90
Purchase #2	$200.82	7.107%	$215.0923	$215.09	$215.10	$215.10
Purchase #3	$229.90	6.262%	$244.2963	$244.30	$244.30	$244.30
Purchase #4	$17.51	3.138%	$18.0595	$18.06	$18.05	$18.10
Purchase #5	$183.29	7.433%	$196.9139	$196.91	$196.90	$196.90
Purchase #6	$193.44	9.504%	$211.8245	$211.82	$211.80	$211.80
Purchase #7	$67.58	4.136%	$70.3751	$70.38	$70.40	$70.40
7 purchase totals =	$1,104.48		$1,180.4762	$1,180.47	$1,180.45	$1,180.50