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	$111.57	9.501%	$122.1703	$122.17	$122.15	$122.20
Purchase #2	$205.43	11.846%	$229.7652	$229.77	$229.75	$229.80
Purchase #3	$162.52	10.504%	$179.5911	$179.59	$179.60	$179.60
Purchase #4	$67.55	3.493%	$69.9095	$69.91	$69.90	$69.90
Purchase #5	$156.62	6.528%	$166.8442	$166.84	$166.85	$166.80
Purchase #6	$184.91	7.869%	$199.4606	$199.46	$199.45	$199.50
Purchase #7	$79.31	3.719%	$82.2595	$82.26	$82.25	$82.30
7 purchase totals =	$967.91		$1,050.0004	$1,050.00	$1,049.95	$1,050.10