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	$119.76	7.615%	$128.8797	$128.88	$128.90	$128.90
Purchase #2	$117.39	8.201%	$127.0172	$127.02	$127.00	$127.00
Purchase #3	$61.26	5.267%	$64.4866	$64.49	$64.50	$64.50
Purchase #4	$147.40	10.307%	$162.5925	$162.59	$162.60	$162.60
Purchase #5	$127.93	6.738%	$136.5499	$136.55	$136.55	$136.50
Purchase #6	$20.35	12.678%	$22.93	$22.93	$22.95	$22.90
Purchase #7	$104.28	9.488%	$114.1741	$114.17	$114.15	$114.20
7 purchase totals =	$698.37		$756.6300	$756.63	$756.65	$756.60