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	$111.76	3.376%	$115.533	$115.53	$115.55	$115.50
Purchase #2	$19.77	6.586%	$21.0721	$21.07	$21.05	$21.10
Purchase #3	$221.55	4.307%	$231.0922	$231.09	$231.10	$231.10
Purchase #4	$221.53	8.122%	$239.5227	$239.52	$239.50	$239.50
Purchase #5	$96.43	3.569%	$99.8716	$99.87	$99.85	$99.90
Purchase #6	$159.73	10.174%	$175.9809	$175.98	$176.00	$176.00
Purchase #7	$240.66	6.486%	$256.2692	$256.27	$256.25	$256.30
7 purchase totals =	$1,071.43		$1,139.3417	$1,139.33	$1,139.30	$1,139.40