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	$111.82	4.108%	$116.4136	$116.41	$116.40	$116.40
Purchase #2	$187.27	5.109%	$196.8376	$196.84	$196.85	$196.80
Purchase #3	$171.85	6.639%	$183.2591	$183.26	$183.25	$183.30
Purchase #4	$232.33	11.821%	$259.7937	$259.79	$259.80	$259.80
Purchase #5	$40.47	4.561%	$42.3158	$42.32	$42.30	$42.30
Purchase #6	$180.77	10.202%	$199.2122	$199.21	$199.20	$199.20
Purchase #7	$194.42	4.316%	$202.8112	$202.81	$202.80	$202.80
7 purchase totals =	$1,118.93		$1,200.6432	$1,200.64	$1,200.60	$1,200.60