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	$103.38	5.677%	$109.2489	$109.25	$109.25	$109.20
Purchase #2	$159.67	12.260%	$179.2455	$179.25	$179.25	$179.20
Purchase #3	$247.83	3.839%	$257.3442	$257.34	$257.35	$257.30
Purchase #4	$98.62	13.795%	$112.2246	$112.22	$112.20	$112.20
Purchase #5	$90.42	4.558%	$94.5413	$94.54	$94.55	$94.50
Purchase #6	$94.79	4.340%	$98.9039	$98.90	$98.90	$98.90
Purchase #7	$204.50	12.527%	$230.1177	$230.12	$230.10	$230.10
7 purchase totals =	$999.21		$1,081.6261	$1,081.62	$1,081.60	$1,081.40