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	$188.78	5.602%	$199.3555	$199.36	$199.35	$199.40
Purchase #2	$144.74	13.358%	$164.0744	$164.07	$164.05	$164.10
Purchase #3	$142.39	10.624%	$157.5175	$157.52	$157.50	$157.50
Purchase #4	$180.84	10.221%	$199.3237	$199.32	$199.30	$199.30
Purchase #5	$108.36	9.198%	$118.327	$118.33	$118.35	$118.30
Purchase #6	$140.68	9.666%	$154.2781	$154.28	$154.30	$154.30
Purchase #7	$81.58	9.809%	$89.5822	$89.58	$89.60	$89.60
7 purchase totals =	$987.37		$1,082.4584	$1,082.46	$1,082.45	$1,082.50