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	$180.39	12.560%	$203.047	$203.05	$203.05	$203.00
Purchase #2	$228.59	5.600%	$241.391	$241.39	$241.40	$241.40
Purchase #3	$79.97	11.570%	$89.2225	$89.22	$89.20	$89.20
Purchase #4	$29.38	8.660%	$31.9243	$31.92	$31.90	$31.90
Purchase #5	$77.87	3.732%	$80.7761	$80.78	$80.80	$80.80
Purchase #6	$107.75	3.725%	$111.7637	$111.76	$111.75	$111.80
Purchase #7	$250.85	13.819%	$285.515	$285.52	$285.50	$285.50
7 purchase totals =	$954.80		$1,043.6396	$1,043.64	$1,043.60	$1,043.60