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	$61.81	8.306%	$66.9439	$66.94	$66.95	$66.90
Purchase #2	$239.71	13.770%	$272.7181	$272.72	$272.70	$272.70
Purchase #3	$74.90	10.238%	$82.5683	$82.57	$82.55	$82.60
Purchase #4	$101.71	12.718%	$114.6455	$114.65	$114.65	$114.60
Purchase #5	$91.69	4.424%	$95.7464	$95.75	$95.75	$95.70
Purchase #6	$113.72	5.578%	$120.0633	$120.06	$120.05	$120.10
Purchase #7	$243.32	8.245%	$263.3817	$263.38	$263.40	$263.40
7 purchase totals =	$926.86		$1,016.0672	$1,016.07	$1,016.05	$1,016.00