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	$247.50	4.242%	$257.999	$258.00	$258.00	$258.00
Purchase #2	$137.89	3.184%	$142.2804	$142.28	$142.30	$142.30
Purchase #3	$241.49	7.396%	$259.3506	$259.35	$259.35	$259.40
Purchase #4	$54.29	3.292%	$56.0772	$56.08	$56.10	$56.10
Purchase #5	$84.52	5.504%	$89.172	$89.17	$89.15	$89.20
Purchase #6	$61.50	6.167%	$65.2927	$65.29	$65.30	$65.30
Purchase #7	$246.73	3.641%	$255.7134	$255.71	$255.70	$255.70
7 purchase totals =	$1,073.92		$1,125.8853	$1,125.88	$1,125.90	$1,126.00