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	$15.31	5.412%	$16.1386	$16.14	$16.15	$16.10
Purchase #2	$47.79	8.144%	$51.682	$51.68	$51.70	$51.70
Purchase #3	$158.31	8.493%	$171.7553	$171.76	$171.75	$171.80
Purchase #4	$82.75	8.231%	$89.5612	$89.56	$89.55	$89.60
Purchase #5	$61.59	4.767%	$64.526	$64.53	$64.55	$64.50
Purchase #6	$105.60	12.620%	$118.9267	$118.93	$118.95	$118.90
Purchase #7	$92.43	10.601%	$102.2285	$102.23	$102.25	$102.20
7 purchase totals =	$563.78		$614.8183	$614.83	$614.90	$614.80