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	$96.67	11.338%	$107.6304	$107.63	$107.65	$107.60
Purchase #2	$69.90	13.786%	$79.5364	$79.54	$79.55	$79.50
Purchase #3	$142.81	9.163%	$155.8957	$155.90	$155.90	$155.90
Purchase #4	$105.40	10.874%	$116.8612	$116.86	$116.85	$116.90
Purchase #5	$171.93	4.153%	$179.0703	$179.07	$179.05	$179.10
Purchase #6	$231.66	10.123%	$255.1109	$255.11	$255.10	$255.10
Purchase #7	$234.91	6.600%	$250.4141	$250.41	$250.40	$250.40
7 purchase totals =	$1,053.28		$1,144.5190	$1,144.52	$1,144.50	$1,144.50