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	$122.73	3.464%	$126.9814	$126.98	$127.00	$127.00
Purchase #2	$138.69	8.808%	$150.9058	$150.91	$150.90	$150.90
Purchase #3	$123.56	6.718%	$131.8608	$131.86	$131.85	$131.90
Purchase #4	$226.94	9.532%	$248.5719	$248.57	$248.55	$248.60
Purchase #5	$11.39	5.247%	$11.9876	$11.99	$12.00	$12.00
Purchase #6	$38.41	10.640%	$42.4968	$42.50	$42.50	$42.50
Purchase #7	$247.35	3.469%	$255.9306	$255.93	$255.95	$255.90
7 purchase totals =	$909.07		$968.7349	$968.74	$968.75	$968.80