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	$115.53	3.433%	$119.4961	$119.50	$119.50	$119.50
Purchase #2	$97.88	9.111%	$106.7978	$106.80	$106.80	$106.80
Purchase #3	$207.56	3.295%	$214.3991	$214.40	$214.40	$214.40
Purchase #4	$162.94	10.274%	$179.6805	$179.68	$179.70	$179.70
Purchase #5	$59.64	3.717%	$61.8568	$61.86	$61.85	$61.90
Purchase #6	$89.62	11.759%	$100.1584	$100.16	$100.15	$100.20
Purchase #7	$233.68	13.429%	$265.0609	$265.06	$265.05	$265.10
7 purchase totals =	$966.85		$1,047.4496	$1,047.46	$1,047.45	$1,047.60